THE AXATOMY OF THE IN THE DOG1

NICHOLAS JAMES AIIZERES Ucpartnitiit of Aiintoiiry, Cnzvemtty of Xtclizgaii Scliool of ;2/cdicmc. Ann Arbor, Mtclatgan

ELEVEN FIGURES

INTRODUCTTOX I

Tiiis paper is n condensation of a clissei t:ition snbniittctl in paytial fulfillmc.~it of tlrc rcqiiireiiieuts for the drgrce of Doctor of Pliilosopliy in the University of Rlicliigaii. I wish to tlimik Dr. It. T. Wootlhuine for Ills interest and aclriec. For the supply of nlatciial tlie author vihlies to e\-pr('\s his appreciatioir to mcmbc~is of the 1)ep:irtiiiciits of P1iTsiolog.y :iiiil PIiar~u:~cologrof tlic Viiirersity of hliclrigan. 2 Present address: Dcpartniciit of Airntoiny, 1V:1pe Ultivcrsity School of JIcdieine, Detroit, Michigan. 283 286 NICHOLAS JAMES MIZERES

MATERIAL AND METILOUS Ten adult clogs, 6 males and 4 fenialm, were injected with ernhalmiiig fluid sooii after death. In 4 speciniens rctl lead was added to facilitate dissectioii of small arteries. The cardiac region was dissected with the aid of a binocular dis- secting microscope.

1)ESCRIPTION The cerviccrl region Soiiidez’ (’31) study of this region ill the puppy is prob- ably the most dcltailecl work iii tlie clog. Both Xonidez (’31) and Finkelstein (1880) described the origin of the clepressor in this area but I failed to find a iiervc which \vould fit their descriptions. It may possibly be very closely iii- corporatcd in the sheath of the vagus iierve near the nodose . 1. The crccszinl cerrictil gcrnglio.12. (fi%q. 1). The cranial cervical ganglion is it large fusiform niass lying adjacent to tlie origin of tlic iiiteriial carotid artc1.y antl tlccp to the lo~vcrmargin of the auditory 1)ulla. It is crossed ventrally by tlie nerve to the carotid sinus and the pharyngeal ramus of the . Its caudal portion lies dorsal to the auricular and occipital arteries antl the hifurcatioii of the coriirnon carotid artery. The riotlose gaiiglioii lies cauclo- lateral to it. I was able to o1)serve inconstant connections to the 9th’ 11th’ and 12th cranial . A coniiectioii to the vagus nerve, just above the nodose ganglion, was ob- served in all 10 specimens. The internal carotid nerve (fig. 1) arises from the cranial pole of the cranial cervical ganglion and lies in close relation to the internal carotid artery as it enters its canal. Tlie artery is convoluted while in the canal and filaments from tlie iii- ternal carotid iierve were observed eiiteriiig the adventitia of the artery. A large nerve (fig. 1) emerges from the caudal pole of the cranial cervical ganglion and forms a clensp plexus n.liich follows the hraiiclics of the external carotid artery. X short thick branch was also observed joiniiig the pliaryngeal raiiiu:, of the vagus ncrvc. Xonidez ( ’31) regarded this liraiicli a:, eiitclriiig the “infei.ior pharyngeal ranius ” of the vagus iiervc’. In the spccirriciis I exarriiiiccl tlic superior and inferior phar- yiigeal ranii \wrc givcw off after this spnipathc~ticconnection entered a “conir1ioii” pharyiigcd ranius. h thin filament arose frorii the cciiti-a1 poi*tioiiof tlic cranial cervical gaiiglioii, coursed hehiiitl tho iiitcrnal carotid artery and nodose gaiiglioii arid eiitt.r(ld tlie first cervical iierv(i (fig. 1). In tlirccl specirrims tliis coniniunicati~igranius mit additiorial filici~to tlie sccoiid aiitl thiid ccrvical nerves ant1 to tlie clcsc(w1iiig cervical ~ier*ve,wlieii piweiit. In t1irc.e of the 10 cases this ramus was absent. C’audally tlic syrnpathctic trunk joiiis the vagus iic’rvc just bclow the nodose gaiiglioii (fig. 1). 111 4 speciniciiis the craiii:il cc>rvical gaiiglioii was obscrvetl scparatccl from the iiotloh~ ganglion bilatci*ally hut in 6 speciniciis t1it.y irere coiiiiectcti lvith short stiaaiicls iaangiiig froin multiple filarricliits to alnioht cornpletcl fusion. A thick mass of fiheix arising from tlic. caudal pole of the ci*aiiial ccrrical ganglion aiid lying 011 thcl hi furcation of thc coniiiioii carotid artery gives rise to iiuiii(~~*ousshort and loiig cloi.sal filanieiits. The short filaments ramify on the wall of the cai.otid sinus or hull) and coirirnoii carotid artery. Tlic long filaments coniprisc two sets. Oiic group courses oii tliv tlorsal wall of the common caieotitl artc1i.p aiid imnifies 011 all pal-ts of tlic niorc caudal portion of thcl ai*tc>ry.The sccoii(I gi-oul) cornpiks what Xoriidm ( ’31 ) calls tlic thpi*oitl iwi*v~ (fig. 1). Fusion of thew filarnciits is variable and in oiily 4 of my specinleiis \\’as a siiiglc iici~eol)serve(l. The thproitl 11e1~vcdescc~iids to\varc\ tlic thyi.oid artci-y as a plesiis (fig. 1 ) \vhich ~*eccivcsan aiiastorriotic filanicnt fi.orn the csteriial laryngeal nerve arid follo\vs tlic artcry tliiwtly into the tliy- roid gland. According to Xonidez ( ’31) the thyroid glaii(1 of the dog is innci~atcdby the cranial crlrrical ganglion ant1 tlic recurrelit laryngeal iierw. I was ahlo in all caws to fintl rccurrciit filwniciiis entcriiig the glaiid. 111 4 CRS;CS soiiic of the tcrniiiial himichrs of tlic recurrent larpiigc~al iicrvo niiiiglcvl with filaitieiits of tlic thyroid plexus. 2. ?’lie r.ccgos?/Inl,trflrefic. frzciik. In the cowse of dissec- tioii, it I\ as o1,servcd that incision of tlic coiiiicctivc tissue slicatli sui.iouiicliiig lmth vagus aiid symp:ithctic t ruiiks al- lo1vcltl tlioir scpai*atioii. By this “ slicath tlissection” it was

INT. CAROTID N

INT MAX A 8PLX. MARGIN OF AUDIT BULLA

EXT CAROTIDA

XI1 N

PHARY NGE A RAMUS OF X

NGEAL PLX.

NT LARYNGEAL N.

THYROID N.

EXT LARYNGEAL N.

VAGOSYMPATHETIC TK

C CAROTIDA THYROID PLX. fon11tl that both trixiiks actually separate a few ceiitimcters cc~1~lialaclto the caudal crrvical ganglioii (fig. 2 E). hi the cixiiial portioii of the iiccli tlic vagus iiewe and sympathetic tlaiil; are coiiiplctcly fuscd. To iiiakc certain this scpara t'1011 aiitl fusioii \\-as iiot a11 ai-tifact of dissectioii, wrial scictioiis 290 SICHOLAS JAMES NIZERES of 6 cervical trunks were made and stained with liematosplin and eosin. It is readily seen that in the middle cervical region a thin comnioii perincurial septum (fig. 3 b) still sepai*ates tlic two trunks (fig. 3 a). In the upper cervical region this coni- nion perincurial septum disappears so that both vagal ailti synipatlietic fibers become interrniiiglecl. The vagosynipa- tlietic trunk sends bi.anclies to the trachea, esophagus, and common carotid artery.

The thorcrcic region By incising tlic cpincurial sheath, the ~xteiit,location, ant1 variations of the raga1 and sympathetic branches forniing a can be ascci*tained with coniparativc eascl. Tliih method of dissection has some application in nerve stirnula- tion. If, in the living animal, tlie caudal cervical ganglioxi can be separated carefully from the vagus nerve with a needle or scalpel, it might be stimulated so that its specific effect on the heart could he determined. The same could be done with the vagus nerve and its branches. The following tle- scription is liasccl on dissection of tlic sheath under a dissect- ing microscope. The figuiw are composite di~awingsant1 thc nerves represented arc those of most frequent occurrence. Because of differences in numher, course, and origin of cardiac nerves in dog and man, it is not possible to LISC iden- tical terminology. Cepl~aladto the caudal ccrvical gaiiglion there is no cardiac nerve in the dog, as was Formerly main- tained by Keng (1893), but later refuted by Sonidez ( ’39) and others. Thus, no superior (cranial) cautiiosymi)wtlicitic nerve can be itlentificd in this foi-m. Soniclez ncvcrthclcss named a superior cardiosympatlietic nerve, sincc ‘‘in sonic instances it (superior cardiosympathetic nerve) map also carry bundles of fibers from the to the deep cardiac plexus or to the anterior wall of tlie atyia.” Although such an ai*i-angerneIitwas founcl in tlic majoiitp of specimens in the present study, it does not secin a valid basis for the namc ascrilwcl to it. So superficial cardiac plexus, comparal)lti to that in ~riaii, could br fomicl iii the clog. Tlicre is a plcsns at the tracheal bifurcation that iiiay be corripai.ct1 to the tlccp cardiac plcsus, lmt, as will be tlcscrihed, its components ai~iiot the same. Schui~awle~\-( ’2i) i~cgarcleclthis plexus as tlic pretracheal plcsus. He classifictl 6 cpicardial plexuses as visualized by the riiethylene blue nietliotl. Actually, only three of these can lw obsc>rvedwith tlie naked eye. These are his plexuses I ailti I1 (right arid left coronary), and IV, wliicli lies in the fold for the ligament of the left precaval vein in the dorsal wall of the left atriurii aiitl extends over the dorsal ventricular wall. Grossly, tlic primary areas of nerrcl distribution for tlie heart may be dcsigiiatcd as pretraclieal plexus, right and left coronary plexuses, doi.sal ventricular plexus, and the fine 1)lcsus 011 tlie dorsal and veiiti*al atrial n-alls. 1. The cnutltrl (w~iuilgtrnglion (figs. 4-71. The caudal cervical gaiiglioii is ahout 3 rrini in width aiitl 3 riini iii length. It lies lateral to, 1)ut in the same epiucurimri, with the vagal trunk on the nieclial aspect of the distal pa1.t of the subclavian artery, betwecii the lercl of the first and second ribs. Its relation with tlic vagal truiik within thc conirrioii clpiiieui.iurii niay vary froiii corripl(ltc3 scipai*ation to almost cornplete fusion (fig. 7). From tlic vciitral surface of the caudal cervical gaiiglioii ai*isc, one to t1irc.e branches that coiitrilmte to the plexus on the hgiiiiiing of the axillary artery (figs. 4-6) aid supply surrounding lyrnpli iiodcs (fig. 6) and common carotid artery (fig. <5). Frorri the axillary plexus aiid the ganglion two or three filaments are sent to the 5th cervical nerve root of the phreiiic ncrve (fig. 6). The origin of these fibers in the dog is prolmbly tlie caudal ccrvical ganglion. Frorri the caudolatcral pole of the ganglion arise the doi*sal and ventral linihs of the ansa subclavia which connect to the stcllltite ganglion. Both limbs of the ansa contrihutc to tlie axillarp plexus. Gray rarni corrirriunicantcs were found to the 7th and 8th and 6th cervical ne~’vcs,in only three specimens. If the arc iiarried according to tlieir ranial connec- tion to the cervical iierves, the caudal cervical ganglion cannot 1)e lioniologizccl with the riiicltllc ccirvical gaiiglioii iii nian u-licrc it wiitls ranii coniniuiiicaiitcs to the 5th aiitl 6th ccli*vical iici*ves (I,aiwll, '53). Since t1ici.c is no infci*ioi*thyi*oitl ai*tcry iii the dog, aiitl tlic ganglion is rclatctl to thc origin of tlir vei*- tchral ai.tcrp, it is pro1)ahly lioniologous to tlic liunian intcrnic- tliatc 01' vci*tcl)ral gaiiglioii, ~vliicliusually scJiicls 1-aiiii coiii- mmiicaiitcs to the 6th ant1 sortietirrics 5th 01' 7th cervical iicrvcs, accoidiiig to Kuntz ( '45). 1,css coiifnsioii will arisc. l)y naming it tlic cauclal cervical gaiiglioii. A filarrielit froni tlie dorsal suifacc of tlic lcft cauclal ccli*rical ganglion, along with a stem fi.orti tlic vagus, i'oriiis ii iiiisctl ii~i~ecowsing bctwceii tlic iiiiioiniiiatc ant1 left sn1)claviaii ;ii-tci*iclsaiitl i*(>acliiiigthe l)ascl of tlic iiiiiorniiiato ai*tcii*ywiitl ventral swfacc of tlic aortic aidi (fig. 4). According to Soiiitlcz ( '39) this iici*vc carries oiic of tlw lwaiiclics of tlic or 1i~i-w.Since it tlocs iiot 1-each the 1icvii.t na11 it caiiiiot lw coiisiclclrctl a cai*cliac iici~ehut iiiay lw i~~fci~1~cvl to as tlic left iniiotiiiiiate iici*ve (fig. 1). Tlic iiglit ii(li*v(bs to the large ai-teiial ivalls \vci~c~strcmcly vai-ial)le iii tlicii- oi.igiii. 111 8 spcciniciis, t\vo scapai,atc iic~'vc1)niitllcs ciiitciwl tlic ~vallsof tlic iiirioriiiiiatc. Tlic msti-al oiic (fig. ,j) aim(^ fi-om tlie tloi.sal sui*faccof tlic cantlal cci.rical gaiiglion iii tuw spclciriiciis, aiicl iii 6 cases it wi*osc by rti~aiisof a stciii that csteiitls fi.oni tlie cauclal cc.i.ricd gaiiglioii to the iwuiwliit cai-tliac iic~n-~(fig. 5). Tliti cautlal nci-vc (fig. 5), pixwilt in all speciiiiciis, ai-osc by irieaiis of scvei*alstcnis f i~)iiitliv 1-iglit rclcui.iwit larpiigeal nerve ant1 tlic iwuri*cnt caidiac ii~rvo. 111 1 spcciiiit.iis both I~(~ITCS\vci*c fouiitl to 1)(1 niultiplc. Tlic imtral iicrvt~,accoidiiig to Soiiirlcz ( '35, W),cai*i*ics tli~ riglit tlcprcssor fi1~1-s.Kotli iiei'vcs may 1)c dcsignatctl as the right iiiiioniinate iicrvcs (fig. <5). Tlic otlici. l~i~aiiclics of tlic cauclal cervical ganglion course in tlic caidiac ~icrvcs. Siiicc t1it.p arc mixed awl difficult to horriologizc with tlic> liurnaii, a clii'fcreiit tcimiiiologp is dc~ilediieccssai*p. A11 the cardiac iicives iiiay be tlcsigiiatcd as cc~rricalaiicl stellat(. cardiac iici*vcs. AGTOXOMIC S E€’,VOUS SYSTEM OF I)OG 293

2. The .~~eiitroiir~tlicrlcer-ricwl ctrrtlitrc. iierrc (fia. 4). The veritromedial cervical caidiac iiei*ve ( Xoiiiclez ’ left suporioi* cardiosyrnpatlietic) is formed from two steins, oiic froni tlic tloi*sal surface of tlie caudal cc~i*vicalgaiiglioii aiitl tlic otlicr from the vagal trunk above the levcl of thc gaiiglioii. Tlicl iiervc lies in the iiiteival hctn-ceii the iiiiiorriiiiatc artc1i.y aiici left vagus nerve. As it tlesccmls onto the ventral surface of tlic aortic aid1 it iweives an atltlitioiial vagal coiitri1)ntioii aiiil scliitls fihers to the aoi*ticwall. It tlicii proccetls ton-arcl tlici I)ulrnoiiary bifurcation, riirdial to tlie ligarriciiturri arteiiosuiii, seiidiiig 1)raiiclies to the pulmoiiai*y artei*ialwalls, prct i.aclic~al plexus, aiid pei-icai-ilium. Aiiotlioi*1)i.aiich courses ai*ouiitlaiit l uiidcr thcl pulnioiiary bifurcatioii to i*cacli tlic pi’etraclical plexus. The veiitrorrictlial ccrvical cardiac iiei~c\vas presciit iii all tlie spccirneiis but vai*ietl as to its origin aiicl 11i.aiiclic~h. In tlie majority of spccirnciis it cai-ricdboth vagal ant1 syiiil)a- tlietic cornpoileiits which ramify over tlic aoi+tic ai~haiitl

1)ulrrioriary bifui.catioii sciicliiig coiiti.il)utioiis, as a rule, to tlicb pi’eti.aclica1 plcsus. Accoi~liiigto Soiiicloz ( ’39) tlie left 1)raiicli of tlic left dcpimsor iicrve is cai-rietl l)y the vciiti~)- nicdial cei*vicalcardiac ii~rvc.Hc illustratctl tho left (l~pi~>h- sol’ iiei~was a sepai*atc iici*vc’ lying 1)etivccii tlic gaiiglioii aiitl tlici vagal trunk. I failctl to fiiitl this i*clatioiisliip iii tlic adult (log. 3. Tlzp i.txti-oltrtertr1 c*ervictrl c.tirdiccc. l;lwi*p (f;,~.4). Tlic vciitrolatcral cervical cardiac iicrvc (Soiiitlez’ left niidtllc cartliosyrripatlietic) is the largest of all tlic caidiac nerv(’h9 approaching the size of the vagal trunk. It arises froiii tli~ caudal pole of tlic caudal cervical ganglion, t3c.scc~ndsIateix! to the vagus, aiid receives and gives aiiastorriotic 1,i.aiicliw to it. Just before reaching thr vciitral surC;tce of thc aoi.tic arch, the nerve hccorries plcxifoim. Reforc it reacliw tlirh ventral surface of the left pulmoiiary artcry, filariiciits fi*oiii the left i*ccurrent laryngeal aiid stellate cardiac ~ici*vcs( fig. 4) join it. Ri*aiiclies arc also seiit to thc. pcricardinni (fig. 1). On reaching the left dorsal atrial wall the plexus follo\\-s tho vestigial fold of the left precaval vein, near the coroiiai.y 294 SICHOL.4S JAMES MIZEllES sinus. After giving filaiiients to the atrial wall it proceeds to tlie dorsal ventricular wall where it spreads out ant1 may be called thc dorsal reiitricular plexus. Accordiiig to Xonidez ( ’39) thc vcntrolateral cervical cardiac iicrvc contains, just Iwlow the ganglion, syrnpatlictic postgaiiglioiiic fibers to- gethci. with a few aflc.rcnts. Thc vagal and i*c~curi~ntfihers that join it later prohahly enter the dorsal atrial wall7 while tho spmpatlietic postgaiiglioiiic fibers eiitclr the veiiti.icular wall ant1 the loft pu1nionai.y plexus. 3. Thp tlorstrl ceri.it~rlctrrtlictc no-i.e (fiq. 4). The dorsal ccrvical cardiac iiervc a]-iscs hy means of one 01’ more fila- niciiits f roni the dorsal surfac(1 of the caudal cei*i-icalganglion aiitl couiws doixal to the left subclavian artery or between tli~latter arid tlie iiiiioniiiiatc artery. On reaching the dorsal surface of the aortic arch it sends filaments to the arch, de- scending aorta, aid pi*eti*achealplexus. 111 its course. it may 1~ multiple or it niay receive additional filaiiients from the voiitral limb of the ansa subclavia, , or vagal t iwik. In three spcviniens it arose from the iiiiioniiiiatc nerve while in one specinien it was absent. 5. Thc reczcrrmf ccrrtlitrc qier1-c (figs. 4, :i,7). The recur- imit cardiac crvc (Noiiidez’ right rriitldle cardiosympathetic) is a large mixed ncrvcL trunk arising from the right recurrent laryngeal nerve as it loops under the right su1)clavian artery. 111 8 spcAcimens it was found to rcceive a contribution from the caudal cervical ganglion, joining it near the loop of the right recurrent nerve. In 4 specimens this svmpathctic con- tribution remaiiietl separate until it joiiicd tlie recurrent ear- cliac nclrvc just before the latter cwterecl the pretracheal 1)lexus. In i specimens it also received a coiitrihution from the vagal trunk near the origin of the recurrelit nerve. As the nerve approaches the prctracheal plexus it receives an aiiastomotic bi*anch from the left recurrent ii(1n-e (fig. 5) and scncls a filament to the rostra1 nerve of the craniovagal 11(~1’~7es (fig. 5). After sending several filamcnts to the pretracheal plexus both dorsal and voii tral to the right piilrrionary artery, the main stem of the nerve, along with a few pi.etrachea1 con- AUTOSOMIC SERVOUS SYSTEM OF DOG 295 trihutioiis, breaks up iiit o a right aiitl left co~oiiwryplexus (figs. 4, 5). The mxtrrc.iit cardiac nerve was present in all specinleiis dissected, but in 4 it raiigetl froni a cloublc stmiid to a plesiforrri arrangement. According to Sonidcz ('39) it coiitaiiis l)regaiiglioiiic, afl'ereiit, and a large iiuniber of sym- ptlictic postgaiiglionic fibers.

Fig. 4 Left side of the cardiac region. 6. The ?*tiycil curdkc w~res(fi,q. 5). Tlic vagal caidiac iic’I*ves arise from tlie I-iglit vagus 1icrvc just 1)elow tlic vcii- tid lirnl) of tlie ansa subclavia. Tlicp riiap 1w groupctl into two sets, tlie cmnial aiitl tlicl caudal vagal cai*tliac I~CITPS (fig. 5). A11 4 iicrvcs anastoriiosctl with each ot!icr at tht. tlorsal aspect of tlic precaval vein. Tlic ci*aiiiovag:.aliiei~cs ciitci. the prct raclicd plexus, wliile the cautlovagal iiervw eiitci*diwctly into tlie iaiglit dorsal atrial wall. Xcitliei* Soiiitlcz ( ’ij9) 1101’ Schnrawlcw ( ’27) rriciitioiictl the cautlovagal I~CI*V(~S.111 .5 spcciriieiis tlie craniovagal cartliac nerves miigetl f rorii three separate sti*andsto a plexus. Tlic vagal cai*tliac iicrv~salso sent filariiciits to the trachea. 7. 7’1.1~strlltite ,qtin,qZio~(figs. +7). Tli~stcllatc ganglion is the lar*gtlst of all the syrnpatlictic ganglia iii the (log. It lics 011 tlie (lorsolateral aspect of thc loiigus colli niusclc cs- tending 1)ctwecii tlie first aiitl third ribs. Tlic thoracic duct lies medial to the gaiiglion. Tlie rarrii conirriuiiicantes of tlic gaiiglion arc conipai~ativclp1a1.g~ ant1 coiistaiit in tlic clog. Tli~ largest gray ranius cxtciitls from the cephalic pole of tlic ganglion, courscs medial to the vcrtcbl.al artery, aiicl at tlic point w1ic1-c~the vertebral artery enters its canal, the iwiiu:, runs over the artery, reaching the 7th ccrvical nerve mot (fig. 6). Here it fuses with tlic nerve to the loiigus colli ~iius- cle (fig. 6). It also coiiti~ihntesa 1)raiicli to the plexus on tlic vcrtcl)l*alartc.1.y. The rainus coinrriuiiicaiis to the 8th ccli.vical nc~vcis variable. 1t rriay lw single 01’ doul~lc,passing ~itlicr side of tlic first ri1) (fig. 6). Tt may also arise in coinriioii with tlic rairius coriiiiiuiiicaiis to tlic first t1ioIw.k nerve. The mixed ranii to T1 and T2 are sliort, wlicreas the ranius to T3 is niucli loiigci*. Quite often, the1-c. is 110 visihlc gaiiglion in tlie syw pathetic tt-uiik at the 4th tlioi.acic levcl, so that tlie stellate ganglion may also coiitrilmtc to the 4th thoracic iie~~e. Van dclii Broek ( ’0s) iiiconipletelp illusti.atec1 a vertcl)ral nerve in tlic clog. It (fig. 6) arises from tlic cephalic pole of tlie stellate ganglioii, citlicr as a scparate iierve or fused with the mrnus to the ‘7th cervical nervt~,and follows tlic incclial surface of the rerte1)ral artcry into its caiial where tlle ~iorvp joiiis tho vcrtebral plcxus. Quite oftcii a separate branch from the ranius to tlicl 7th cci.vica1 iicrvc ciitoiwl this plexus. The aiisa suhclavia (figs. 4, 6) is foi~~i~~l1)p tlic splitting of tlie sympathetic tiwiilr hy tlie suliclaviaii ai*tcli*y1xtn.cc.n the caudal cervical aiitl tlic stellate ganglia. Its veiiti*alaiitl tlorsal

Fig. d Bight side of the cardiac region. 29s SICHOL.4S JAMES MIZEHES limbs niay again be split. Sonitlez ( '39) described ganglionic aggrcgations in the ventral limbs of the ansa in histological pi*cparations. By dissecting away the sheath a ganglion of observable size was found in thiw of niy specimens (fig. 2). Both iirrihs of the ansa contribute to thc asillary plexus. The right aiisa suhclavia differs f'i*oni the left since its ventral limb map connect diiwtly to the stellate gaiiglioii (fig. 7 A), or it may run within the slicath of the vagus nerve (fig. 7 C). Other variations were also found (fig. 7).

VAGOSYMPATHETIC TK

TO LONGUS COLLi M.

RAMUSCOMM TO

T3 Ti' FROM'C.506

8. The stelltrte ctrrtlitrc. +~~wes.The left stellate cardiac wive (fig. 4) is variable, raiigirig from a compa1*atively thick nerve to a fine plexus, and in 5 specirriens it was ahsent. In 4 specimens it arose from the stellate ganglion and in one it arose from the ventral linih of the ansa sul)clavia. It smt filaments to the left , venti-olateral cervical cardiac nerve, and to the dorsal ventricular plexus. The riglit stellate cardiac nerves (figs. 5, i)(Xonidez' riglit infcrior car- diosyrnpathetic nerve) arose (Lither from the stellate ganglion, from both the ganglion and ama subclavia, or from the ganglion, aiisa suhclavia and vagal trunk. Tlicir nunilwr ranged from one to 5 iiervcs, eitlicr fused or separate. Tlicy AUTOXOMIC SEBVOUS SYSTEM OF DOG 299

~OUIW over the ventral surface of thc hasc of the preca~al arid azygos veins, contributing to the right pulrnonary plexus aid the right dorsal and ventral atrial n-alls. Sonitlez ('39) found no distinct nerve from tlie right stellate ganglion, but mentioiled the possibility that postganglionic fibers niiglit course within the ventral limb of the ansa aiicl join those froni tlie caudal cervical ganglion ( '39). In 5 cases only oiic or tlvo filaments were present, and in one three large iiei~eb aiwsc directly from the caudal cervical ganglioii with contribn- tioiis from the ventral limb of the ansa subclavia and vagur ncrvc (fig. 7 A). These nerves entered the right atrial walls aiitl pulmonary plexus, thus intlicatiiig that in tlic one sI)clci- rticii the stellate cardiac nerves may course through the caiitlai cc.ivical ganglion and only appear as branches of tlie ganglioii. It is also probable that when the stellate cardiac nerves ap- pear as oiily one or two filaments, thcl rest of the iicrves riiay coui'se as postganglionic fibers through the caudal cervical gaiiglion and in the sheaths of the vagal cai-tliac nerves (fig. 7 1)). $1. Cur d i t r c uer r e s b el o 21: t h e s t e 11(1 t e g (I ng 1i o ?a. IoncSCU, Scliurawlew, Xonidcz and others tlcscrihetl cardiac 11c~i.v~~ ai*isiiig 1)elow the stellate ganglion in both mail ant1 clog. Although tlicre is agreeriicnt about rrian, eritlcncc is con- flicting concerning the dog. Ionescu ( '28) fonnd no bralichr~:, in one dog, a few 011 the right side in two, anti a €PW on both sitles in one. Scliurawlew ( '27) illustratetl 1)raiiches froni T:! aiitl T3 on the left side only. These iiei-v(~s\v~i*e looked for \\-it11 great care in all the specirnens tlisscvAec1 in this study. 111 oiily two cases one or two filarrients were found cnte~ing tlic pulrnonary plexus, but none passed to llic heart ivall. I)efiiiitc filarnciits to the dcsccncling and thoracic aorta 1vcn~ found arising coiistantly from all tlir ganglia or intcrgangii- oiiic rarrii of the thoracic sympathetic truiil; tlo~vnto T12. In many cases these filaments (fig. 4) were intcrconncctcd in a plcsiform nianner with an occasional ganglion 11ear the ~vall of the aorta. 300 SICHIOLAS J.4ME:S 3IlZEI:ES

10. The ~dr.rusc.sof fhe fliorcccic. rrgioir. The asillmy picisus (figs. 46) is forrned by filariieiits arising from both Iini1)s of the aiisa sulxlavia, the cauclal cci.vica1 ganglion, and viii.ial)ly from the stellate gaiiglioii. It lies 011 the asillary

C. RECURRENT CARDIAC N

Fig. 7 Xiglit si(l(1. V:iri:itioiis of tlic cniit1:il cervical ~iitlstel1:itc ganglia, ansa subclnvia am1 r:ntlinc ii(1rvc~. 111 A, tlic q~iii(wri;il>lientli is slio~vn iii re- lation to the I~~I'PCS. artciy aiitl seiicls subordinate plcxuscs to its liraiiclics. The asillary plexus is also coiiiiectetl with the 5th cervical root of tlie phrenic iiei~e(fig. 6). Tlic vei.tcbi*al plexus (fig. 6) lies 011 the vertebral artery as it ciitci*s its caiial. It is forrricd ljy the vertebral iierve (fig. 6) and by variable filanichiits from tlie gray rariius conirriuiiicaiis to the 7th cervical nerve (fig. 6). It niay send gray rarrii comniuiiicaiitcs to tlic upper cervical iicrves emerging through the intcrvertehral foraniiiia, ljut I could not definitely ascei-taiii this by gross tlisscction. The ~iglitpulmonary plexus (fig. 5) is foi.mcc1 by vagal lirniiclics aiid filanieiits from the stellatr cai*tliac Iiciws. The caudal poi-tioii of the plexus is forrnetl 117 direct hi*aiiclics of tlicl ~iglit vagus iierve. Tlie left pulmonary plexus (fig. 4) is foriiictl liy filaments €rani the dorsal ventricular plexus, as it coursed ovcr thc left pulnioiiary artery, and from 1)ranclies of tlic left vagus aiid stellate cardiac nerves. The caudal poi3ioii of thc 1)lesus is fornicd directly by the left vagus ncrvc. The pi'('- tiwheal plexus (figs. 4, 5) lies v~ntralto tlic traclical hifurca- tioii ant1 dorsal to the right pulriionai-y ai.tc1.y. Soiiic of its 1,raiiclics also ran rciitral to the artcry (fig. 5). It i.(whivcs filarrielits froni the left recurrent, veiitronicdial cci*vical ca~ diac iicrvc, tlic reeurreiit cardiac nerve, tlic dorsal ccrvical cartliac nerve, and the ci-aiiiovagal caidiac nervcs. The plexus sends filanients to the dorsal atrial walls ant1 to tlic riglit and left coronary plexuses. Tlic coroiia1.p plesusw (figs. 4, ,j) arc extensions of the pi-ctrachcal plexus. Tlic principal contrihutioii comes from tlie recurrent cardiac iierv~(fig. 5), whose niajoi. stem secnis to foim tlw plexuses directly. Fila- nients froni both p1cxusc.s also ciitci*the 1-oot of tlic asccwling aorta (fig. 5). The main trunks of tlic plexuses follo\v thc course of tlie right arid left coi-oiiary arteries into the veil- ti*iculai-wall. The dorsal ventricular plexus (fig. 4) hegiiis as a iictwoi.B of filarrielits 011 the ventral suifacc of the lcft pulmonary artery and vein coursing over the left dorsal atrial lvall in relation to the coroiiai-y sinus, ant1 finally eiite~iiig and spreading out on the left dorsal ventricular wall. It is cIc~i.ivecImainly from the ~-cntrolateralcervical cardiac iierve with niiiior additions froni the left iwuiwiit 1ai.ynpal nerve, as that nerve courses uncler the ligaiiicwtuiii atclriosmii, arid from the left stellate cai-cliac iiei*w. 11. The thortrcic ccrgzrs tirid syrr~potheficf).llEili. The dog having 13 ribs, 13 levels are to 1)c coiisitlerecl. The syiipa- thetic trunk is coiistaiit in its ranial coriiicctioris to the spinal nerves, but the o1,servahle ganglia are not. The ganglia liegin at the 4th thoracic level and continue to tlic 9th thoracic level. From the 9th to the 13th thoracic level the truiik a1)- pears as a single strand. In all the specimens l)i*anchc~srcvxli the aorta from tlie ganglia or intc.rganglioiiic ranii of the lcft trunk. These braiiches are iiitcrcoiinectecl in a plesiforni iiiiiii- iier and in 4 speciriieiis rninnte ganglia were i)rcsent aiiioiig the branches. On tho right the bimiches are fon-ci. aiitl imiiifv on the wall of the azygos vein and esophagus. Both vagi couiw doi*sal to the pulmonary roots, send branches to the esophagus, and each iriinieiliately divides into a ventral aiid a dorsolatcral branch. The right veiitrnl bimicli is longer than the lcft. In 4 specinieiis the shorter left l)rancli was double. A fusion of hotli ventral 1)raiiches occui*red in tho upper third of the csophagus in three specirneiis and in 7 spcciniens the fusion occurred in the middle third of the esophagus. This vciitral fusion forms the ventral gastric iierve (fig. 8)' which courses on the ventral surface of the esophagus arid enters the abtlonieii through the esophageal hiatus. The dorsolatcral brarich of both vagi courses at first lateral to the esophagus and then dorsal in the lower thirtl of the esophagus. Fusion of these dorsal braiiches to form the dorsal gastric nerve (fig. 8) occurs in the lower third of the esophagus, so that the dorsal gastric nerve is much shorter than the ventral nerve. Direct 1)raiichcs from 130th clorsal ant1 ventral braiiclies of the vagus nerves enter the esophagus. Dowgiallo ( '28) described an esophageal plcsus in the dog. Like Hilsabcck arid Hill ('30), I could not demonstrate this plexus. AUTONOMIC NERVOUS SYSTEM OF DOG 303

The abdowziml region

1. The vagus nerve. The right arid lcft vagi enter the abdominal cavity as the dorsal aiid ventral gastric nerves. The ventral gastric nerve, after passing the esophageal hiatus, breaks up into a short plexus. From this plexus two groups of branches arise, a hepatic arid a gastric group. The hepatic branches, two or three in number, leave this short plexus aiicl course through that part of the lesser ommturn near the car- diac region of the stomach mingling with the filaments lying 011 the interlobar branches of the hepatic artery (fig. 8). The gastric branches, three or 4 in number, supply the ventral surface of the stomach. The largest stem of the gastric brariches follows the lesser curvature, sending branches to the pyloric portion and ending near tlie pyloric sphincter. A number of filaments arise from the ventral gastric branches and anastoniose with the sympathetic plexus on the branches of the left gastric artery (fig. 8). The dorsal gastric nerve (fig. S), shorter than the ventral, follows tlie dorsal surface of the cardiac region of the stomach. After sending a few branches to this area it breaks up into a plexus through which the esophageal arteries (fig. 8) coume. The branches of the plexus anastomose with the plexus on tlie celiac aiid proximal portion of the left gastric arteries (fig. 8). In 5 specimens separate dorsal gastric branches from this plexus were fol- lowed to the hepatic and cranial nieseiiteric plexuses. The main stem of the plexus follows the lesser curvature, sending branches to this area and to the dorsal surface of the pyloric portion of the stomach where the nerve disappears into its wall. In 5 specimens, I found the dorsal gastric nerve sciiding several hepatic filariierits (fig. 8) through the gast rophrenic lizament to the plexus on the terminal hranclies of the hepatic artcry. Neither Hilsabeck and Hill ('50) nor PIZcCrea arid D'Arcy ( '25) mentioned these hepatic branches. 2. The abdominal plexuses and collateral gcinglitr. Thc ccliacomescnteric plexus surrounds the roots of the ccliac and cranial nieseiiteric artelk. Due to its density it foi.rr~s 304

m a tight ring around both arterial stenis. It sends subordinate plexuses along tlie hranclies of the celiac and cranial mesen- teric arteries, which are iianied according to thc. branches 011 which they lie. Thc celiac (figs. S-9) aiitl single cranial niescnteric (figs. 8-9) ganglia lie in the nieslies of the plexus. Although both celiac ganglia receive filaments from tlic dorsal gastric nerve the right ganglion rcceives more direct branches (fig. 8). The plexus on the hepatic artery (figs. 8-9) is dense aid often conipletely covers its adveiititial surface. It is formed mainly by tlie right celiac ganglion and dorsal gastric iic~ve. The plexus also sends branches that course ventral to the portal vein (fig. 8) arid eiiter tlie pancreas. From that part of the hepatic plexus that lies near the origin of the pyloric arteries diwct branches are smt to the common bile duct and pyloric portion of tlie stomach (fig. 8). The plexus on the gastroduodenal artery sends filamciits to the duodenum, pailereas, and terminal portion of the common bile duct (fig. 8). The right gastric and gastroepiploic plexuses supply the right portion of the greater and lesser curvatures of the stomach. The plexns on the cystic artery supplies the cystic duct, gall bladder, aiicl proximal part of the common bile duct. Tlic terminal hraiiches of tlie hepatic artery carry the ter- iiiiiiatioiis of thc hepatic plexus and, if dixscctcd with caw, these terminal filaments may he seen to enter the liver lobes tlirougli the interlobar arteries and to aiiastoniosc with the he- patic branches of the ventral gast~icnerve (fig. 8). The splenic plexus (figs. 8-9) fo1lon.s tlic artci.y and scAnds hraiiches to tlic spleen, body, arid tail of tlie pancreas, and to the left portion of the greater curvature of the stomach by way of tlic left gastroepiploic artery. It is formcd niainly by the left celiac ganglion. Direct pancreatic arteries from the celiac artc>ry also carry filaments to the pancreas (fig. 8). The Icft gastric plexus (figs. 8-9) on the left gastric artery enters tlie left portion of the lesser curvature, fundic, and cardiac arCas of the stomach. Near the cardiac area, the filaments on the arteries ariastomose with the branches of the ventral gastric nerve (fig. 8). This plexus is formed by both celiac 306 NICHOLAS JAMES MIZEGES ganglia and the dorsal gastric nerve. The bilateral phrenic plexus (fig. 9) was found to arise by direct branches from the celiac ganglion. After entering the upper portion of the muscular crura, the plexus was observed to connect with the phrenic nerve (fig. 9). Although a phrenic ganglion is de- scribed by Larsell (’53) in man, no ganglion was observed in this area in the dog. In one specimen a separated ‘‘ phrenic” ganglion from the left celiac ganglion occurred along the phrenic artery. The bilateral adrenal plexus (fig. 9) is a dense network of filaments that is completely covered by the adrenal gland. Within the meshes of the plexus, be- sides many arteries, minute adrenal ganglia are found. These ganglia lie along branches running from the celiac ganglia into the adrenal gland. The rest of the plcxus is formed from the celiac and splanclinic (fig. 9) ganglia and from direct branches arising from the thoracic splanchnic nerve near the splanchnic ganglion. The renal plexus (fig. 9) is fornied from I~ranchcsarising either from the splanchiiic and aorticorenal ganglia or from the aorticorcnal ganglia only. Among its bundles one or two renal ganglia (fig. 9) were found in all my specimens. The dense plexus descends to reach the wall of the renal artery as it enters the renal sinus. The unpaired cranial inesentcric plexus (figs. 8, 9) is formed by the cranial mesenteric ganglion with contributions from both celiac gang- lia. Branches of the dorsal gastric nerve w~realso observed to enter the plexus directly (figs. 8, 9). Branches of the plexus followed the branches of the cranial mesenteric artery to the small intestine and part of the large intestine. According to Schmidt ( ’33), in the dog, the vagal fibers are distributed at least as far as the distal portion of the transverse colon. The unpaired intermesenteric (aortic) plexus (fig. 9) is a group of long parallel bundles lying on the ventral surface of the aorta connecting the cranial and caudal mesenteric ganglia. In 8 out of the 10 specimens, one of these bundles became greatly thickened several centimeters below the cranial mesenteric ganglion, and extended caudally to con- nect with the caudal mesenteric ganglion. Trumble ( ’34) and AUTOSOMIC NERVOUS SYSTEM OF DOC: 307

Learmonth and Markowitz ( ’29) clesignatetl this tliickciicd bundle as tlie ‘‘celiac root7’of the inferior (caudal) iiiesenteric ganglion. The term is not a valid one since this thick bundle has no connection with the celiac ganglion and the term “root” is misleading. It is only a thickeiied part of the in- termesenteric plexus, sirice in all my specinieiis at least two or three thinner strands were associated \vith it. It was fouiid to vary in position and fine filaments from the plexus were observed entering the adverititia of the ahdominal aorta (fig. 9). The internal gonadal plexuses (fig. 9) may he grouped into two sets, a proper and an accessory group. The proper plexus, associated with the intcmial goiiadal artery, was pres- ent in all the specimens. A gonadal ganglion (fig. 9) asso- ciated with the proper plexus was observed in three speci- mens on the left side and in one specimen 011 the right side. In another specimen a ganglion was observed near the hilum of the ovary. The accessory gonadal plexus, associated with an accessory internal gonadal artery (fig. 9) was fouiid in 3 specimens. Rut in three specimens, although the artery was absent, this accessory plexus took origin froni tlie aortic plexus at the same level and, associated with a ganglion, de- sceiided and came into relation with tlic proper left iriteriial gonadal artery which had a higher origin than usual. Thus the accessory plexus was observed in 8 specimens. An ac- cessory gonadal ganglion (fig. 9) was associated with this plexus in three of the 4 females and 5 of the 6 males. The plexus on the caudal mesenteric artery consists of two or three tliick strands which follow the branches of tlie arte1.y and form a dense meshwork that can be followed cranially to the branches of the cranial mesenteric artery. Caudally, this plexus was followed on the hemorrhoiclal vessels and some of its filaments were observed to anastomose with dorsal filaments of the hemorrhoidal part of the pelvic plexus (fig. 10). Learmonth and Markowitz ( ’29) mentioned “lumbar colonic” nerves which apparently run independently of tho caudal mesenteric plexus. No specific mammal was nientionetl 308 NICHOLAS ,JAJLES MIZERES in tliciir n.oi.1; aiid I coald iiot fiiitl these iici'ves iii any of iiip specimens. 3. 7'1ic tkoruck spltr~.ic?i~iic9iilerz.c. In iioiic of tlicl spcci- riiciis tlitl I ol)seive iicrvcs compai*al)le io the limiiaii 1cssc.r aid least splaiichiiic ~iervcs. T1ici.e \\-as only oiic 1ai.g~ah- tloniiiial synipatlietic iici~ethat eniclrgrtl fi.oiii thc. tlioiwic synipathctic truiik. It may be dcsigiiatrvl as tho thoracic splaiiclinic iirrvc (fig. 9). It is larger tliaii the truiil; itself aiicl cours('s uiitl~i*tlie iiiedial lumbocostal aidi and 1atc.i-a1to tlic crus of tlic tliaplii.agrri. Tli~iicrvc sciitls filariiciits to tlw tlioracic aorta hcfoi~.passing the riiai-gins of the 1unil)ocostal ai.clics (fig. 9). ,Just 1)cfoi~~joiiiiiig tlicl splaiichiiic gaii %lion (fig. $I), the thoracic splaiiclniic iitli*v(' sciids tliiwt filaiiiciits to thc atli*ciial gland. Thc. lcvcl of (lni('i*g('iicrfi*oni thc. tlior- acic sympathetic ti-uiik occui*i*ctliii ispeciiiiciis fi-orii tli,>13th tlioiwic ganglion aiid iii tliiw spcv3rnciiis fi-om the ti-uiik lw- tweii tlir 13th tlioi*acic ant1 first 1nnil)ar levels. Ti1 '7 spcci- ~iiciisthe thoracic splaiicliiiic iici~eWLS coiiiicctctl to tlic first 1urril)ai- splancliiiic ii~i~cby a varia1)lc iiurnbrr of fiiicl fi!arric.rits. Iii 4 specinieiis it also iwclivctl a s11oi.t coiiti.il)utio~i fi*orii the. spriipatlietic ti.uiil; at tht. first lunii)ai* h-~l. 4. The lzirirhtrr S,lJill~J(ith?tictririik triid its hrcci1chc.s. Tli~ luml)ai*spptlictic tiauiik aiid its vai*iatioiis liavcl l)ccii cai~ fully stutliccl l)y Jlclilci., Fisclic.1. aiitl Xlcsaiirlcr ( '52). Tli~ 1urril)ar truiik 1)cgiiis as a thiii stmiit1 arisiiig front tlic first lurnbai* ganglion aiitl courses uiitl:~i*tlic nicvlial luiiihocostal aidi, latcral to the ciwra aiitl nicthl to tlic psoas ~iiusclcs. The. trunk aiitl ganglia 1)wonic tliickei* aiitl loiigei- caudall~-. Th~.r*oai~ 7' 1unil)ar vcrtchi-acl iii tlic (log. M~lilri-( '52) statcvl that out of 100 (logs only 37F slion-rd a ganglion at each lmii- 1)ai. levcl. In 6 of riiy spchciniciis fusioii occui*wtl lxltivccii tlicl first aiicl sccoiitl luriil)ai* ganglia, uiiilatc.1-ally 01' I)ilatci.ally, with occasioiial fusioii iii otlici- I)ai*ts of tlic truiik (fig. 9). Accoi~liiigto 3[clilci* ( '32) the lowwt pwgaiiglioiiie outfloiv of the syrripathotic truiik occuiwtl at tlic. 4th lunil,ai* 1rrc.l iii 65% of his spccirneiis aiid at thcl 5th 01- 6th 1unil)ai- lclv~1iii tlic remaining :Ir>r/c. ('autlally the 1uiiil)ai- syrripat1i:ltic trunks fuse in a variable fashioii. According to Neliler (’52) fnsioli most often occurrcd at the 7th luriibar lcrcl. This \\.as true in 6 of my specimens. From the first through the 5th lunilmr lcvcl clefinitcl visceral branches of tlie syiripathetic truuk have 1)c~cufouiitl iii all 10 specirriens. Tlic first lunihai* splaiicliiiic iiervo (fig. 9) aristls from the first luriibar gaiiglioii or trunk. 111 H spcciniciis it was fouiid coiiiiected to the thoi*acicsplaiicliiiic iiervc~by iiicaiis of several fine filaments. The nerve, which may be hplit, courses under the lurribocostal arches, over the ci‘ura of tlic diaphragm aid ahove the renal artcry, and usually cii t t1i-s the aorticoreiial aiid cranial niesenteric gaiiglia, iiiclatliiig the iutermeseiiteric plexus. The secoiid 1iirnl)ar splaiicliiiic iierve (fig. 9) arises from the syrripathctic ti-unk or gaiiglioii at tlie secoiid lnnibar level arid COLI~SCS clolwil to the wiial artery arid emerges on its ventral surface aiitl seiids filmii(wts to the intermrscnteric plexus or to the cranial ~ncseiitcric ganglion. It usually sends a filarriclnt to the acci?ssoi*y goiiadal ganglion if there is oiic. In three cases it snit hi-aiiclics to the I-cnal plexus, ant1 in two others it sent filariieiits to tliv aorticorciial gaiiglioii. The third lurribar splancliiiic iicn-(~ (fig. 9) arises from the third luml~rgaiiglioii or synipatlictic ti-uiik, and courses toward the vmtral surface of the a1,tloni- iiial aorta caudal to the renal artcry. It tlivitles into sevrixl filarrierits just before reaching the upper portioii of tlic iu- termesenteric plexus. In two specirriciis it \\-as foiiiitl to lw double, in which case filaments were also sent to the secoiid lurnlmr splaiicliiiic nerve, and from oiie of these 11crves fila- ments wcre found entering the left aorticorciial ganglion aiitl renal plexus. In two specimens filarriciits wcre seen eiit(3riiig the accessory goiiadal ganglion aid in tn.o cascs filaments eii- tcrccl a proper ovarian ganglion. In auotlier two cascs, unilateral 1)ranclies from thc third 1uml)ar splanclinic i1ci’vt’ wt~reohserved entering the cranial riicscntcric ganglion. Tlic 4th lumbar splaiichnie nerve (fig. 9) arises froni tlie 4th lunl- bar ganglion or level of the trunk aiid descends just al~ovc tlie proper gonadal artery to enter the iutermesenteric ant1 310 RICHOLAS JAXES XI1ZE:HES

/)// RRANCHES FnRENlC N

1 13 G T GASTRIC A 1 HEPATIC A -

4111 4 PLANCHNIC N PHRENIC A ADRENAL G 8 PLX RT CELIAC G

SPLANCHNIC G 82

CRANIAL MESENTERIC G G.

RENAL PLX - RENAL A - ACC GONADAL G

INTERMESENTERIC PLX.

GONCDAL G.4

IN1 GONADAL A- 8 PLX PROF'ER

CAUDAL MESENTERIC G

RT HYPOGASTRIC N -

Fig. 9 The lunibosacral sympatlietic trunk, its braiiches, and tlre collateral ganglia. AUTONOMIC NERVOUS SYSTEM OF DOG 31 1 proper gonadal plexuses. This pattern was constant in all 10 specimens. The 5th lunibar splanchnic nerve (fig. 9) arises from the 5th lumbar ganglion and courses just below the proper gonadal artery to enter the caudal mesenteric ganglion directly. In only one case was this nerve absent. Although filaments from the 6th and 7th lumbar levels were variable, when present, these splanchnic branches always entered the caudal mesenteric ganglion. In two cases, a ganglion was observed on the course of the 7th lumbar splanchnic nerve. In another two specimens a ramus arising from a left 7th lunibar nerve followed the right hypogastric nerve to the pelvic plexus. These variable , along with direct fibers from the 6th and 7th lumbar ganglia, sent fila- ments to the postcaval vein (fig. 9) and iliac arteries.

The pelvic region 1. The hypognstric nerves (figs. 9-1 1). The hypogastric nerves of the dog arise from the caudal pole of the caudal riiesenteric ganglion. The two nerves course retroperitoneally over the common iliac arteries and over the promontory of the sacrum to enter the . After reaching the lateral sur- face of the rectum they anastoniose with the pelvic nerves (fig. 10) to form a dense pelvic plexus (fig. 10) lying under the pelvic peritoneum as it is reflected over the upper part of the rectum. In 8 specimens fine filaments were observed connecting both hypogastric nerves and the caudal mesenteric plexus (fig. 10). Only a few filaments from the hypogastric nerves to the iliac vessels were observed. 2. The pelvic nerves (figs. 10-21). Tlic pclvic nerve arises by one or two stems from the first, sccoiid, and third sacral spinal nerves. It courses under the parietal peritoneum deep in the floor of the pelvis. After reaching the lateral wali of the lower rectum it anastomoses with the descending hypogastric nerve. From this anastomosis the dense pelvic plexus takes origin and sends branches to the pelvic viscera. In three specimens the pelvic nerve appeared doublc unilater- ally. 312 SICHOL.\S JAMES JLIZEHES

5'. Tlic pelcic 1d(~.xiis(figs. 10-11). Tlic Iwlvic plcsus is a deiise iiet\vork of filanieiits arising fro111 the fusion of tlic hypogastric ancl pelvic iie~*vcs.It lies iicai*the lateral surface of the rectuiii aiicl is interniiiiglecl with tlic 1)i.aiiclics of tllc urogenital artery (fig. 10). TT-itliiii its iiics1ic.s arc fo~uida variable 1iunil)cr of ganglia. The su1,tlivisioiis of tlici pelvic

LT HYPOGASTRIC N

VAS DEFERElS

GNASTOMOSiS OF HYPOGASTRIC 8 PILVIC hS

EMORRHOIDAL A

81.ADDER a PLX ANASTOMOSIS OF MORRHOIDAL PLEXUSES GA NGLION IN PELVIC PLX

PROSTATE GLD NT PUDENDAL N a a URETHRA a PLX

HEMORRHOIDAL PLX LT CRUS OF PENIS plexus are iiarried according to the organ iiiiicrvatctl. sucli as, prostatic, vaginal, urethral, aiid heniorrlioidal plcsuscs. Tlir uriiiary bladder aiid its intrinsic and cxtviiisic plexuses wew cai-cfully studied hy Sclia1)adascli ( '26). Tlic cst riiisic plexus is readily seeii as a fine iietu-ork with sriiall gaiiglia coiic(1ii-

HORN OF UTERUS

HYPOGASTRIC N

BLADDER 8 P

UROGENITAL A BODY OF UTERUS

HEMORRHOIDAL PLX

trated near the iiecli of the urinary bladder. The fernalp urogenital plexus was described as subdivided into vaginal and uterine plexuses by 1Iedowar ( '27). Although the pelvic organs innervated by thc pelvic plexus arc different in the male and female, the plexus itself was found to l)e tlic same. 314 NICHOLAS JAMES MIZERES

All the pelvic organs receive a rich nerve supply. The plexus 011 the male urethra anastomoses with filaments from the in- te~~ialpudendal nerve (fig. 10). The hemorrhoidal plexus seiids ascending branches into the dorsal rectal wall and anastoniotic filaments over the ventral surface of the rectum to reach the opposite pelvic plexus. It also sends a few fila- ments which anastomosed with the sympathetic plexus on the hemorrhoidal vessels (fig. 10). Mitchell ( ’35) aiid Telford and Stopford (’34) described in man the path of the sacral parasynipathetics as coursing through the niesocolon at right angles to the branches of the inferior mesenteric artery. This relationship was not found in any of the 10 dogs. In the dog the sacral parasympathetics appeared to ascend in the mus- cular wall of the rectum and also within the sympathetic plexus of the hemorrhoidal vessels. 4. The sacrctl (fig. 9). As mentioned previously the 7th lumbar ganglia are either fused or coii- nected by a number of short filarrients so that the sacral sympathetic trunks lie close together. In conjunctioii with this close relationship I found some form of horizontal fusion between the . Although the ganglia were ex- tremely variable, gray rami communicantes were found to enter all the sacral spinal nerves. Fine filaments were also observed ramifying on the middle sacral artery. A “” mentioned by Bfehler ( ’52) and Miller ( ’49) could not be found in any of my specimens. The sympathetic trunks were observed to extend into the tail region.

SUMMARY AND COIi;CL17SJOSS The gross anatomy of the autonomic nervous systeni of the dog, excluding the cephalic region, is described aiid illus- trated on the basis of 10 complete dissections. The following findings warrant emphasis : 1. The cranial cervical ganglion sends branches to the common carotid artery and its terminal branches, including the thyroid artery. It also sends separate filaments to the thyroid gland. It is intimately associated with the nodose AUTONOMIC NERVOUS SYSTEM OF DOC: 315 ganglion and sends a contribution to the pharyngeal ramus of the vagus nerve and a ramus communicaiis to the first cervical nerve. Other connections to the cranial nerves were infrequent and variable. 2. The vagus nerve and sympathetic tiwnk are fused in the upper but separate in the lower cervical region. Both nerve trunks are enclosed in a common epincurial sheath. 3. No cardiac plexuses comparable to the human arc pres- ent in the dog. Instead, a pretracheal plexus I-eceivesbranclics f rom the craniovagal, recurrent cardiac, left recurrent lar- yngeal, dorsal cervical, and ventromedial cervical car- diac nerves. The ventrolateral cervical cardiac nerve and the left stellate cardiac nerve form the dorsal ventricular and part of the left pulmonary plexus. The recurrent cardiac nerve forms the main parts of the right aiid left coi*otiary plexuses. The caudovagal cardiac nerves enter primarily the right dorsal atrial wall. The right stellate cardiac n~rvcs are variable in course and number and enter the dorsal and ventral right atrial walls aiid right pulmonary plexus. Right and left innominate nerves enter the large arterial walls. The stellate ganglion sends rami communicantes to C7, ('8, T1, T2, T3, and sometimes to T4, in addition to a vertebral nerve. The ventral limb of tlie right aiisa subclavia usually i'uiis in the sheath of the right vagus nerve. The caudal cervical ganglion is probably comparable to the human intermediate or vertebral ganglion. Besides contributing to the cardiac nerves, it also sends filaments to the phrenic nerve. No car- diac nerves below the stellate ganglion were observed. 4. The ventral gastric nerve, shorter than the dorsal, sends branches to the liver and ventral surface of the stomach, and anastomotic filaments to the plexus on the funclic and car- diac branches of the left gastric artery. The dorsal gastric nerve sends branches to the dorsal surface of the stomach. It also contributes to the celiacomesenteric plexus and to the plexus on the proximal portion of the left gastric artery. In 50% of the specimens the dorsal gastric nerve sends branches 316 KICHOLSS JAMES MIZERES to the liver. Filaiiieiits of the dorsal gastric nerve can hc followed into the hepatic ancl cranial mcseiiteric p1exust.s. 3. The stoniach not oiily receives 1)raiiches from tlic plt.xuscis 011 the gastric aiid epiploic artelk hut also clii-ect filarnents from the gastroduotleiial plmus which enter tlic pyloric portion of thc stomach. The paiicreas i*cc~iresits supply from the plexuses 011 the splciiic, paiicreatic, wild gwstrotluotlciial ai.tericis with additional tlii*ect contributions from the hepatic plexus. The coninion hilt duct receives lwaiiches from the plexuses on the hanclies of the gast1.o- duodenal and cystic arteries. Thc gall 1)laddcr recc4ves fila- riients fi-orn tlie plexuses 011 the cystic and hraiiclies of the hepatic artery. The adrenal gland recciws its iniicrvatiou fr.oni the celiac, aorticoi*ciial, ancl splaiiclinic ganglia, aiid direct filanients from the tlioi.acic splanclinic nerve. Tlie iwial plexus is foimied by tlir aorticorenal antl renal ganglia. A pi’opcr and a left acccbssory gonatlal plexus are connected with the intermesentcric plexus. ,411 accessory left gonadal ganglion is rriorc often present than a propcbr ganglion. Th:\ iiiternieseiiteric plexus receives lwaiiches f i*oiri the secoiid, third, antl 4th, and sonietimes first lunibar splanchnic nerves. It sends filaments into the adventitia of the ahdominai aorta. 6. The single thoracic splanchnic 1i~rv(3emerges from tlie sympathetic trunk at the 13th thoracic level aiid terminates in a splanchnic ganglion. The first lumbar splanchiiic iicrve sends filaments to the aorticorenal aiid cranial mesentc~ric ganglia and intermesenteric plexus. The second lurnhar nerve enters either the cranial niesentei-ic ganglion or the inter- rnesenteric plexus, and sonietinic.s scwds filaments to the renal plexus and aorticorclnal gaiiglion. The third lumhar splaiich- riic nerve enters the intcimeseiitei-ic plexus ancl sonietiniw sends hranclies to tlicl sccond lurnhai. ii~i~e,and cranial mesen- ory, or propcr gonadal ganglia. The 4th lunibar splanchiiic nerve enters th(1 iiitc.rnitlsciitcric and proper goiia- (la1 plexuses. Tlie 5th lumbar nerve enter.s the caudal mescii- tcric ganglion directly. Splanclniic hrwnchcs frorn thc 6th ancl 7th lumbar levels arc variahlr or absent. Fusion of tli~ Innihar synipatlietic trmiks usually occuix at thc ‘7th 1urril)ar 1?\‘e 1. ‘7. The hypogastric aiid pelvic iic~v~smiitcl 1o foi-ni a pc~lvic Idcxus. An aiiastoiiiosis occsr:, hetweeii thc licriiorrhoidal plexuscs 011 the ventral surface of the rcctuiii. A fcw filaments fi*oin the heniorrhoitlal plexuscs also coiiiiwt \\-it11 tlic syni- pathctic plexus 011 the hernorrhoitla1 wwcls, indicating that the sacral parasynipathetic fibc~smay ascciitl iii tho symp- tlicltic pcii*iavtcrial plexus. Sacral paraspnipatlietic branchcs also ascend on tlic dorsal aiid ventral walls of tlic rcctuiii. The pelvic plcxus of tlic fernalr is siniilar to that of the nialc. Fen. filanieiits w(xi*efouiicl to eiitcr tlic atl\-cwtitia of th:. iliac \‘c s s el s. 8. Gray raiiii coiiirnuiiicaiites arc scliit to all tlie saci-a1 s1)iiial iiervw aiitl small filainoiits to thc saci.al artery. So <

I,I TEIi.4 T V K E (’I T.EI ) ]%LADLE\;,0. (’. 1948 To1)ogr:iphical Aii:it.omy of tlrr Ikfi. Olircr :iiitl Iioptl, Loiiclon aiid Ecliiibnrgli. ~)O\VGIALLO, S. 1). 1928 Tlir esoplingc>nl nerves of tlic (log. Ztschr. f. Ahat.11. ~iitwicklniiffsgescli.,h’3 : 591-595. ELLEXEEHGER,W., AN) 11. R~CM1891 Aiiatoniic~ ties Ilaiidrs. Vcr1:ig YOU P:iul Parry, Sly., 10 Heilcni;ri~iistlnsse,Hcrlin, 563-669. FISKELSTBIX, A. 1880 1)er Ncrl-us depressor Iirini Jlcnsclicii, liaiiiiiehc~i, Haiidc, bci der 1i:itze uiid ilriii I’fcrtlc. Arch. f. Anat. unid Phyiol., 245-252. HILSAHECK,J. R,., ANI F. C’. HILL 1950 Aii:itomp of tlie thoracic. wgus in the dog ant1 a tcchriique for its iiiterrnptioii. Proc. Sac. Exp. Riol. RII~ Med., $9: 633-637. , l)., AWD 31. EWACHESCU1928 ~‘iitrrsuchuiigcn bci Siiugetiereil und Meiisclicn iiber (lie ails dem Hrustgreiizstraiig des Spmpathirus untcr- 1i:iIl) r1f.s Gniiglioii stcll:iti~m riitsprurigcrieii Hcrziicweii. Ztsehr. f. L411:1f.,

MCCREA, E. D'ARCY 1935 The abdominal distribution of the vagus nerve. J. Anat., London, 59: 15-40. MEDOWAR,J. L. 1927 Die Nerven des Uterus und der Vagina des Hundes. Ztschr. f. Anat., 86: 776-785. MEHLER,W. R., J. C. FISCHERAND W. F. ALEXANDER19.52 Anatomy and varia- tions of tlie lunibosacral sympathetic trunk in the dog. Aiiat. Rec., 113: 421436. MILLER,M. E. 1949 Guide to the Dissection of the Dog. Edwards Bros., Ann Arbor. MITCHELL,G. A. G. 1935 The innervation of the distal culon. E4inburgh Med. J., 42: 11-19. NONIDEZ,JosB F. 1931 Innervation of the thyroid gland. 11. Origin and course of tlie thyroid nerves in the dog. Am. J. Anat., 45: 299-329. 1935 The aortic depressor nerve and its associated epithelioid body, the glonius aorticuni. Am. J. Anat., 57: 359-260. 1937 Distribution of the aortic nerve fibers and tlie epithelioid bodies (supracardial ' paraganglia ") in the dog. Anat. Rec., 69 : 299-313. 1939 Studies on tlie innervation of the heart. Am. J. Anat., 65: 361-401. SCHARADASCH,A. 1926 Die Nerven der Hamblase des Hundes. Ztschr. f. Anat., 86: 730-754. SCHMIDT,C. A. 1933 Distribution of the vagus and sacral nerves to tlie large intestine. Proc. SOC. Esp. Biol. and Med., 50(6): 739-740. sCHURA4WLEU', A. IT. 1827 Dic Herznerven des Hundes. Ztschr. f. Anat., 86: 683-697. TELFORD,E. D., .4ND J. S. R. STOPFORD1934 The supply of tlie distal colon. Brit. Med. J., 1: 572-574. TRUMBLE,H. C. 1934 The plan of the visceral nerves in the lumbar and sacral outflows of the autonomic nervous system. Brit. J. Surg., 91 : 664-676. VAN DEN BROEK,A. J. P. 1908 Untersuchungen uber den Rnn des svnnnthischen Xervensyteins drr Szngetiere. Tlieil 1, Morpli. Jnlirb., 37 : 229-233.