Meatus Is Not Yet Developed. the Par-Occipital and Maxillary 1 Parsons, " on the Anatomy of Petrogale Xanthopus Compared with That of Other Kangaroos," Proc

Home , Hyoid bone

ON THE ANATOMY OF MACROPUS RUFUS. By BER- TRAM C. A. WINDLE, D.Sc., M.D., M.A., Professor of Anatomy in Mason College, Birmingham, and F. G. PARSONS, F.R.C.S., F.L.S., F.Z.S., Lecturer on Comparative Anatomy at St Thomas's Hospital, London. THE following notes are based upon the dissection of two specimens of Macropus rufbs. The first (A) was a young animal taken from the pouch of its mother: it measured thirteen inches from the tip of its snout to the root of its tail, and the lower incisors were the only teeth projecting beyond the gum. The second specimen (B) was an apparently full-grown animal: as will be seen from the condition of the bones, however, it was not fully matured. As one of us has recently given a full account of the anatomy of Petrogale xanthopus,' we have used this for purposes of comparison, and have dealt mainly with such points in our present specimens as differ from those already recorded in the other. OSSEOUS SYSTEM. In connection with this part of the anatomy, we propose to confine our observations almost entirely to the conditions of the bones dependent upon age, as the osteology of the adult form has been already sufficiently dealt with. Skull.-This agrees with the characteristics by which the skull of Macropus differs from that of Petrogale, except that the infra-orbital canal is double on both sides in A, and on one in B. When compared with the adult skull, one is struck by the much greater convexity displayed by the more immature form (A) in the roof of the cranium, as also by the shortness of the facial portion, owing to want of antero-posterior growth of the maxilla. The tympanic bone also forms much more of a bulla than it does in the adult, and the tubular part of the bony meatus is not yet developed. The par-occipital and maxillary 1 Parsons, " On the Anatomy of Petrogale xanthopus compared with that of other Kangaroos," Proc. Zook. Soc., 1896, p. 688. 120 PROFESSOR WINDLE AND MR PARSONS. zygomatic processes are quite rudimentary. In all these respects the older specimen (B) conforms to the characters of the adult skull. In (A) the four parts of the occipital bone are ununited, in B the basi- and ex-occipitals have fused, but the supra-occipital is still a separate bone. There is in A a distinct lateral fontanelle below the posterior inferior angle of the parietal; this has disappeared in B. The Atlas has the whole of the ventral arch in A, between the articular processes, cartilaginous, and the posterior arch has still a thin plate of cartilage in the median line. In B there is a considerable unossified interval in the ventral arch, only a fissure marking the position of the cartilaginous central part of the dorsal. In A the grooves for the sub-occipital nerves are not yet converted into foramina: one of them is completely so in B, whilst the other still presents a fissure between the two parts.

FIG. 1. Axis of young Macropts rmfm (B)-dorsal aspect. The Axis in A is composed of four portions: (1) the odontoid; (2) the centrum; (3 and 4) the two sides of the neural -arch. Only the dorsal part of the transverse process and vertebrar- terial canal is ossified. In B (see fig. 1) the axis consists of the following portions: (1) the lower epiphysial plate; (2) the odontoid, with the anterior articular processes; (3) the centrum and sides of the neural arch, united into one portion of bone; (4) a small diamond-shaped bone intercalated between the odontoid and the anterior part of the centrum, visible both on the ventral and dorsal aspects, which apparently represents the upper epiphysial plate of the centrum. ON THE ANATOMY OF MACROPUS RUFUS. 121 The other vertebrae have the same centres as the human foetus presents at birth. The Hyoid bone is interesting in both specimens, as presenting elements of the second and third bronchial arches in different conditions of development. In the younger specimen the second arch is completely cartilaginous, and is represented by the two cerato-hyals, which are triangular in shape and have their bases applied to one another, whilst their apices are prolonged outwards and forwards towards the base of the skull. In B these are of the same shape, but the basal portions of both sides are ossified, though the two bones are separate from one another and from the thyro-hyals. These last in A are ossified laterally, but remain cartilaginous near the middle line, whilst in B the ossification is complete, and no traces of cartilage remain in this part of the arch. But in this specimen a bony hexagonal basi- hyal exists as in the adult form, and the four other parts of the arch are bound to it by fibrous tissue. The Clavicle has only the diaphysis ossified in A. The Scapquia in A has only two centres, one forming the ala and spine, and the other the rudimentary coracoid. In B a third centre is added between the opposed surfaces of the coracoid nucleus and the glenoid fossa. In A the Humerus has no secondary centres, but the supra-condylar foramen is completely ossified, and is wholly formed by the diaphysis. In B there are secondary centres (1) for the two tuberosities, (2) for the inferior articular surface, (3) for the external condyle, (4) for the internal. In A both Radius and Ulna have the shaft ossified, and there is an epiphysis present for the lower ends of the bones, whilst in B there is also an upper epiphysis, which is almost completely united to the diaphysis, the lower being still detached. In the corpus of A there are bony centres for the following elements, scapho-lunar, cuneiform, pisiform, trapezium, os magnum, and unciform, but the trapezoid has as yet no centre. The metacarpals and phalanges have cartilaginous heads and bases, only the diaphyses being ossified. In B the carpus is fully ossified, each of the metacarpals has a nearly united epiphysis for the head, and each phalanx one in a similar condition for the base. In the Os innomhinatum, of A there are centres for ilium, ischium, and pubes, together with one median nucleus for 1929 PROFESSOR WINDLE AND MR PARSONS. the sub-pubic bone, and there is no cotyloid bone. In B the three primary parts of the bone are firmly united, and there is a distinct sub-pubic bone. There are alsQ secondary centres for (1) the crest of the ilium, (2) the tuberosity of the ischium, (3) a minute but perfectly distinct centre for the apex of the prominence of bone which projects from the centre of the ile(- pectineal line. The marsupial bontes do not appear to have been ossified in the younger specimen; in the older one they were fully so. The Femur in A has no upper epiphysis, but in the lower end there are two centres of ossification, one for either condyle. In B the condition of this bone is exactly as has been described in the specimen of Petrogale. The groove showing the line of union of the two centres forming the lower end is, however, very evident, and shows that the earlier condition had been the same as that of A. The Tibia in A has two epiphyses at its upper end,-a large one for the greater part of the head, and a smaller one for the anterior part of the same. In B these two epiphyses are almost completely united to one another and to the diaphysis. In both specimens there is an ossified lower epiphysis. The Fibula in both has upper and lower epiphyses. In the foot both specimens show the existence of two centres of ossification for the os calcis, one for the body and the other for the posterior part of the tuberosity. In the younger specimen one centre of ossification was noticed in each case for the astragalmus, cuboid, navicular, and ecto-cmuneiform, all which are fully ossified in the older individual. In the great fourth toe there are centres for the shaft and head of the metatarsal, and for the shaft and base of the phalanges. In the case of the other three toes in A only the shafts of these bones have any ossific deposit in them, but in B there is also an epiphysis for the head of each metatarsal.

ARTICULAR SYSTEM. The articular system of Macropus closely resembles that of Petrogale, so that it will only be necessary to mention the few points in which differences exist. In the wrist there is a strong (O THE ANATOMY OF M:ACROPUVS RtJvUS. .123 fibro-cartilaginous band, which passes from the ulnar side of the lower end of the radius to the adjacent part of the cuneiform, which we are inclined to think represents the otherwise absent triangular fibro-cartilage. Again, the peg-like lower end of the ulna is received into a cavity formed partly by the cuneiform and partly by the curiously-shaped pisiform, and not solely by the cuneiform, as in Petrogale. The knee-joint presents the following differences:-(1) The external lateral ligament consists of two parts, of which the superficial is posterior in position above and anterior below; it is also narrower inferiorly, and attached to the anterior end of the outer aspect of the head of the fibula. The deep part, which is flatter, and placed more anteriorly above, passes under the superficial, to be inserted partly beneath it and partly to the more posterior part of the outer aspect of the head of the fibula. In neither of these parts are the fibres continuous with those of the Extensor longus digitorum. (2) The internal lateral ligament is very closely attached to the semi-lunar cartilage. (3) The tendon of the popliteus contains a very strong fibro-cartilaginous fabella, which is placed above the head of the fibula, to which it is attached, and on which it moves freely. It is with this fabella that the large gastrocnemial fabella, to be more fully described in another section, articulates. (4) The synovial membrane extends a full inch upon the anterior aspect of the femur. The arrangement of the external lateral ligament of the ankle- joint, which differs in some respects from that of Petrogale, is as follows. It consists of the following parts:-(1) from the outer malleolus to the outer part of the os calcis; (2) from the apex of the malleolus straight down to the prominence on the os calcis beneath it: this part can be easily separated into deep and superficial layers; (3) from the outer border of the lower (i.e., articular) aspect of the fibula, passes inward and backward between the articular surfaces of the fibula and of the above- named prominence, to be inserted into the lower edge of the outer aspect of the astragalus just below its articular surface; (4) from the inner aspect of the lower end of the fibula, passes between the articular surfaces of that bone and of the astragalus, and is inserted into the anterior end of the outer calcanean prominence. Thus these two inter-articular ligaments 124 PROFESSOR WINDLE AND MR PARSONS. cross one another inside the joint, one intervening between the corresponding surfaces of the fibula and calcanean prominence, and the other between those of the same bone and the lateral facet of the astragalus.

MUSCULAR SYSTEM. In this section only those muscles have been mentioned whose arrangement presents some difference from that already recorded for Petrogale. Muscles of the Head and Neck.-'The platysma is almost apo- neurotic in the neck, but considerably thicker and more muscular over the face where it extends on to the Lasseter covering the facial vein. It is also well developed over the parotid, where it extends to the lower and outer part of the pinna, forming the depressor auris. The other muscle of the pinna is at once a retractor and rotator. It is a strong sheet of muscle, arising from a tendinous intersection between the muscles of opposite sides, which form a V as they pass forwards and outwards to the ear, into the whole of the posterior and mesial aspects of the base of which they are inserted. The retractor labii superiors is in two parts: (1) upper and superficial, terminates in a fine tendon, which is inserted into the lip near the angle of the nose; (2) deeper and narrower at its origin, it broadens out as it passes forwards to be inserted into the whole of the remainder of the lip and its angle. The origin of both of these parts is from the lower and anterior border of the orbit. The sterno- and cleido-mastoid muscles are united, and the 11th nerve pierces the latter. The Omo-hyoid is thin and ribbon-like; it has a feeble central tendon in A, but none in B. It is inserted into the junction of the dorsal and middle thirds of the anterior cephalicc) border of the scapula. There is a very large and well- marked stylo-glossus, a feeble stylo-pharyngeus, and stylo-hyoid is fused with digastric in A, separate in B. Omo-trachelian arises from the 1, 2, 3 cervical transverse processes, and is inserted into the acromion and adjacent part of the spine of the scapula for about one-fifth of its length. It is covered at its insertion by the cacullaris. Scalenus ventralis is absent, s. longus passes from the 4, 5, 6 cervical transverse processes to the 2 and 3 ribs, s. ON THE ANATOMY OF MACROPUS RUFUS. 125 brevis from the 5, 6, 7 processes to the first rib. Theie are recti capitis dorsctles superficialis et medius. Muscles ofthe Anterior Extremity.-A few fibres of the anterior part of the unsegmented rhomboid sheet reach the occiput in B, so that there is a rhomboideus capitis: in A the muscle belongs only to the neck, though it very nearly reaches the occiput. Serratus colli (lev. anguli scapulae) and serratus magnus form a single sheet, which is in A attached to all the cervical vertebrae except the atlas, and to the ribs from the first to the seventh. In B it is attached to all the cervical vertebrae and to the first five ribs. Infra-spinattus exceeds supra-spinatus in size. TLeres llbinor is a small muscle, quite distinct from infra-spinatus, as it is in Petrogale and the Wallaby, though not in the Great Kangaroo. The arrangement of the pectoral muscles is substantially that met with in Petrogale, but the abdomino-pectoral is not so well marked as in that species. The sidbscapularis is not supplied by the suprascapular nerve as in Petrogale, but by two branches from the posterior cord, the lower of these also supplying teres major. Coraco-brachialis brevis is alone present, according to the general rule in Kangaroos, and arises in common with the coracoid portion of the head of the flexor longus cubiti (Biceps). Macalister found this muscle divided into two slips in Xlacropus ruficollis, a condition which was not present on either side in our specimens of rufus. Flexor longus cubiti (biceps) can easily be divided into a ventral coraco-radial portion, which is fleshy at its origin and tendinous at its insertion, and a dorsal (deep) gleno- ulnar part, which is tendinous at its origin and fleshy at its insertion. In A both heads of flexor brevis cubiti (brachialis anticus) are present, as they are in Petrogale; in B we could not find any separation into two parts, though, as the muscle was very thick and strong, and arose from a considerable portion of the anterior aspect of the bone as well as from its outer side, it is probable that both were represented, though in a fused condition. Palmaris longs in B ends in a strong flat tendon, which crosses the anterior annular ligament, and after giving a slip to the pisiform, ends in the fascia of the hand. From the ulnar side of the expansion rise the fibres of the palmaris brevis, a large and distinct muscle. From its radial side comes off a 126 PROFESSOR WINDLE AND MR PARSONS. bundle of muscular fibres, which is inserted into the uhnar side of the head of the metacarpal bone of the pollex, and evidently represents the flexor brevis of that digit. There is a strong sesamoid cartilage on either side of the hand, that on the ulnar side overlying the pisiform, that on the radial the base of the first metacarpal and the trapezium. The anterior annular ligament stretches between these two cartilages, and from the radial cartilage arises the abductor pollicis. In A three lumlt'ri- (ales are present, but only two in B, viz., those between the tendons of index and medium, and medius and annularis. Flexor sublimis digitorurn is a very tiny muscle, which ends in tendons for the four inner digits on both sides in B, whilst in A it is distributed, as in Petrogale, to index, medium, and annularis only. As indeed might be expected, the number of tendons belonging to this muscle is clearly variable, since Macalister and Meckel found the same number as existed in our specimen B. The ,flexor profundus digitorum consists of the following parts :-(1) centralis, small but quite distinct; (2) condylo-ulnaris, the largest head, almost immediately unites with (3) linaris proprius, which is larger and extends farther up the foramen than (4) radicals proprius, which is quite a small muscle. There is no condylo-radialis. The above-mentioned portions of the muscle fuse, and form a tendon, which has a remarkable fibro-cartilaginous thickening of an ovoid shape on its ulnar border, where it plays against the pisiform and unciform. The tendon then divides into five stout slips, one for each digit. In the hand there are superficial adductors for pollex, index, and minimus, which arise from a common head attached to the carpal bones. Macropus therefore wants the adductor annularis which is met with in Petrogale and in the Wallaby. Supinator longus appears to be a variable muscle in the Kangaroos. In Petrogale it was inserted into the dorsum of the scaphoid on both sides. Macalister describes it as being inserted into the first metacarpal in the Wallaby, and into the trapezium and first metacarpal in the Great Kangaroo. In our specimen A the insertion of the muscle on both sides is into the lower third of the radius. In B it is on one side inserted into the dorsum of the scaphoid, whilst on the other no trace of the muscle is to be seen. Extensor carpi radialis longior is inserted ON THE ANATOMY OF MACROPUS RUFUS. 1 27 into the dorsal surface of the metacarpal bone of the index. It is much smaller than the brevior, from which it is distinct. According to Macalister, the two muscles are fused and terminate in two tendons, which are inserted into the 2 and 3 metacarpals, a condition which MacCormick believes to be the normal arrangement in the Marsupialia. We are of opinion that a very little pulling will show that in almost every case where these muscles are said to be fused, they will be found to be really separate. -Extensor minimi digiti sends a slip to annularis in A which we did not see in B. Muscles of the Posterior Extremity.-Ilio-tibialis (sartorius), tensor fcascice femoris, ecto-gluteus, and flexor cruris lateralis (biceps) form one continuous sheet. Ecto-gluteus arises from the posterior sacral and anterior caudal vertebrae: it has no insertion into the femur, but joins a deeper layer from the anterior caudal transverse processes, to form a tendon which is inserted into the outer side of the patella. Flexor cruris lateralis arises from the tuber ischii, and very slightly also from the fascia over the caudal muscles: it is inserted into the fascia of the leg, and by its connection with the ecto-gluteus also into the patella. It is then continued down as a strong band, which, after uniting with a similar downward prolongation from the semi-tendinosus, forms with it a sheath for the posterior surface of the tendo Achillis, upon which it is prolonged downwards as far as the os calcis, where it becomes attached partly to that bone and partly to the sides of the plantaris tendon. There is a tenuissimus present. The gractilis arises slightly from the base of the marsupial bone, but in other respects it resembles the condition met with in Petrogale. Semni-membranosus is very closely connected with the adductor mass; in fact, on its superficial aspect, there is no obvious separation between the two until a short distance above the point of their insertion at the knee. A deeper dissection, however, shows that the ischio- femoralis, a very well developed muscle, lies between the two, near the femur. The last-named muscle, though closely connected with the adductor mass, associates itself with the hamstring group, by the fact of its obtaining its nerve supply from the large hamstring nerve which comes off from the back of the great sciatic. It is, in fact, apparently a dismemberment 128 PROFESSOR WINDLE AND MR PARSONS. from the deep surface of the semi-membranosus. In specimen A the gemelli are arranged in the same manner as in Petrogale, but the condition is not quite the same in B, where these muscles are represented by some of the fibres of the obturator interns, which arise very close to its point of exit from the pelvis, which cannot be said to constitute a separate muscle. It is probably this condition of affairs which led Meckel to state that the gemelli are absent in Kangaroos. Tibialis anticus is a very large muscle, which is inserted into the bases of the internal metatarsals, and slightly also into the ento-cuneiform. Extensor longus digitorum in A resembled Petrogale; in B, as has already been mentioned, it differed from the fact that its tendon was not prolonged up to the femur,-probably only an individual varia- tion. It ends in a single tendon, which forms a wide expansion over the large central toe only. Expansions from this constitute the dorsal parts of the capsules of the metatarso-phalangeal and inter-phalangeal joints. From the deeper surface of this muscle, and very closely connected with it on one side of B, arose a second part, which developed a tendon which passed under that of the long extensor to be inserted into the outer toe. This condition was not met with in A. Only a peroneus longus was met with in A; B having a p. quinti in addition. The outer head of the gastrocnemius possesses a remarkably large fabella, already mentioned as articulating with that of the popliteus. This was crescentic in shape, and in the older specimen measured 2'5 cm. from one cornu to the other. At the upper cornu is a distinct tubercle, from which, as well as from the external condyle above, arises the plantaris, which is thus a double-beaded muscle. From the anterior (convex) surface arises the outer head of the gastrocnemius, or rather one head of it, for a second comes from the patella. From the inferior cornu arises in B a distinct strong muscle, which joins by its tendon that of the gastrocnemius in the lower third of the leg, to constitute the tendo Achillis. This arrangement was not noticed in the younger specimen, which appeared to conform to the condition of Petrogale. We think that this third head represents the otherwise absent soleus, which may, however, as in B, regain its independence, though taking origin from the large fabella, instead of from the head of the fibula. The inner ON THE ANATOMY OF MACROPUS RUFUS. 129 head of the gastrocnemius has also, in the older specimen, a fabella, of much smaller size than that of the outer head, and differently situated. This fabella lies below the origin of the muscle from the back of the condyle of the femur, and between the muscular fibres and that bone, upon which, therefore, it plays. The plantaris, arising as above mentioned, is a very large muscle, exceeding in size the outer head of the gastrocnemius. After being joined by the expansions from the hamstrings, its tendon passes over the os calcis into the sole of the foot. There it gives off a slip to form a perforated tendon for the outer toe. The main portion, after this slip has been given off, divides into three parts, of which the two lateral are attached to the spurs on the plantar surface of the large sesamoid plate which under- lies the tarso-metatarsal articulation, whilst the central becomes the perforated tendon of the fourth toe. Popliteus is very much as in Petrogale, but the portion which arises from the semilunar cartilage is almost completely segmented off from the remainder. There is a very distinct rotatorfibulae. In the sole of the foot there are three muscles: (1) a thin band on the inner side, which ends in tendons for the 2 and 3 toes: this, which is functionally an adductor secundi et tertii digitorum, probably represents the adductor hallucis, which, in the absence of that toe, has acquired attachments to those nearest to it; (2) adductor minimi digiti, absent in A; (3) flexor brevis quart digit, much the largest muscle: single at its origin, it divides into two parts at its insertion into the spurs of the sesamoid plate of the metatarso-phalangeal articulation.

VASCULAR SYSTEM. The heart in A is exactly similar to that of Petrogale; and even at the early age of the animal from which it was taken, there are no signs of a fossa ovalis or other fetal structure. In B the condition is similar, except that in the right ventricle there is a very distinct though small moderator band attached just below the ventral musculus papillaris of the valve. From the base of the dorsal musculus several fibrous cords spring, which traverse the cavity; and still nearer the apex there is a VOL XXXnL (N.S. VOL XII.) I 130 PROESSOR WINDLE AND MR PARSONS. second muscular band, which passes from the dorsal to the ventral wall. The thymus in A occupies its usual situation: it consists of two lobes, each of which is about 75 mm. in length. The aorta and great vessels are as in Petrogale. The common carotid bifurcates opposite the cephalic end of the larynx, and at this point the superior thyroid is given off, the lingual and facial arising very shortly afterwards. The subclavian and axillary arteries are as in Petrogale. The brachial gives off a small branch some little way above the supra-condylar foramen, which descends to the surface of the forearm, and may correspond to the human radial. The remainder of the artery divides into ulnar and posterior interosseous, as in Petrogale. The abdominal aorta and its branches are arranged as in Petrogale, and the condition of its caudal end, which is that already described by Owen, assumes considerable interest in the light of the observations of Young2 on the middle sacral artery. The aorta divides into three branches opposite the disk between the fifth and sixth lumbar vertebrae. Of these branches the lateral are the two external iliac arteries, whilst the central, which passes still farther caudalwards, divides into the two internal iliac arteries, and gives off the caudal artery. It is customary to describe the two internal iliac arteries as branches of the caudal; but assum- ing, which we believe to be the case, that Young is correct in his view, it would be more accurate to say that in the Kangaroo the external iliac arteries are direct branches of the aorta, which subsequently divides into the two internal iliacs and gives off the caudal. The femoral artery gives off no definite external circumflex, but there is an internal circumflex. After giving off the last-named vessel, the femoral divides into saphenous and popliteal, as in Petrogale, and both of these trunks are distributed as in that animal. The veins are arranged as in Petrogale, the vena cava posterior occupying a position ventral to the iliac arteries. NERvous SYSTEM. The arrangement of the cranial nerves and of the cervical plexus is the same as that of Petrogale, and there is a depressor I " Abnormalities of the middle sacral artery, and their morphological significance," Jour. of Anat. and PIys., vol. xxxi. p. 169. ON THE ANATOMY OF MACROPUS RUFUS. 13.1 nerve, which lies close to the vagus. As regards the brachial plexus, it has been already mentioned that the subscapularis is not supplied (as it is in Petrogale) by the suprascapular nerve. The coraco-brachialis is supplied by a slender twig which comes from the outer cord before the outer head of the median has become detached from it. The median itself is formed in the axilla as in man, and not low down in the arm, as in Petrogale. It passes through the supracondylar foramen, and in the upper part of the forearm it gives off the radial, which goes, as in Petrogale, to the dorsal side of the radial three and a half digits. The importance of this method of the origin of the radial nerve, in relation to Paterson's well-known views as to the brachial plexus, has already been alluded to in the paper on Petrogale. The rest of the course of the median is as in Petrogale. The ulnar comes off in the axilla, and gives off in the upper part of the arm a small internal cutaneous branch, which supplies the skin over the olecranal region. There is also a larye internal cutaneous, which is derived from the internal cord. The only point upon which stress need be laid in connection with the lumbar plexus is the high origin of the internal cutaneous nerve of the thigh, which can be traced almost entirely into the third lumbar nerve.

DIGESTIVE SYSTEM. There are eight transverse ridges on the roof of the hard palate. The soft palate is thick and large, and possesses a long narrow uvula, which appears to contain very little muscular tissue. The epiglottis is intranarial. The tongue in both specimens possesses three circumvallate papillae: the fungiform and filiform papillae are scarcely developed in A, whilst in B they are present in normal numbers. In both, feeble transverse folds indicate the position of the papillae foliatee, which are better developed than in Petrogale. The tongue has no transverse ridges in either specimen. The salivary glands correspond in all particulars in B with those of Petrogale, but in A there is, in addition to the ordinary glands, a further pair of large size lying at the root of the neck, and meeting one another in the mid-ventral line (see fig. 2). They are pyriform in shape, with 132 PROFESSOR WINDLE AND MR PARSONS. the stalks directed towards the head, and their broader posterior ends overlap the pectoralis major. Histological examination proved that these glands were. salivary in their nature, but we did not succeed in tracing the termination of their ducts. The stomach possesses a bifurcated greater cul-de-sac: it has also two very strong longitudinally running muscular bands, one

-. 3

-6.

FIG. 2.-Ventral aspect of neck of fetal Macropus rufus. 1, Extra salivary glands. 2, Sublingual glands. 3, Ext. jugular vein. 4, Sterno-hyoid muscle. 5. Mylo-hyoid muscle. 6. Pectoralis. on either side, which cause the greater curvature to be exceedingly sacculated. The smaller curvature, which measures twelve inches in length in B, as well as that part of the stomach which intervenes between it and the longitudinal bands, is smooth, and devoid of sacculations. A third longitudinal band, running along that part of the lesser curvature which is nearest to the pylorus, causes the formation of an ON THE ANATOMY OF MACROPUS RUFUS. 133 antrumn pylori. There are no glandular patches in the interior of the stomach around the opening of the uEsophagus. The intestines, like the stomach, closely correspond to the description given of this part of the anatomy of kangaroos by Owen. The caecum is straight and non-sacculated, and contains several Peyerian patches, some of which are of large size. The splcee presents the usual tri-radiate appearance. The liver (see fig. 3) consists of right lateral and central, left lateral, spigelian and caudate lobes, and the gall-bladder rests between the two

9 FIG. 3.-Liver of Macropus rfu8w, seen from below. J.L, Right lateral. R.C, Right central. L.L, Left lateral. Sp, Spigeliaii. C(aw, Caudate lobes. C.b, Gall-bladder. f, Falciform ligament. portions of the right central. In thus describing the lobulation of the liver, we are aware that we are adopting a different method from that of others who have dealt with the marsupial liver. For these writers the gall-bladder is the line of demarca- tion between the right and left central lobes. We cannot agree with this method of looking at the matter, since we believe that the falciform ligament, with its contained umbilical vein, is the morphological line of division between the right and left halves of the liver, The gall-bladder is an offshoot from the bile-duct, 134 ON THE ANATOMY OF MACROPUS RUFUS. and may be absent in some mammals: it ought not, therefore, to be looked upon as having any significance in the division of the liver; and when it is present, it always rests either upon the right central lobe or between its halves. We regard, in the present instance, that part of the liver which is to the left of the falciform ligament as representing the left central lobe: it is comparatively small, quite destitute of any fissure, and the left lateral lobe must, therefore, be considered as absent. The kidneys are nearly on the same level, though the left is slightly anterior in position. In A they show slight transverse depressions, which are not visible in B. These depressions may be indications of lobulation, but no lines of division extend from them into the interior of the organs. The adrenals are small flesh-coloured bodies (measuring in A 1 inch antero-posteriorly and 1 inch transversely), which lie a little anterior to the kidneys, but are not connected with them. The older specimen being a female, the internal genitalia were examined.. They corresponded to the descriptions given by Owen and by Lister and Fletcher.' The last-mentioned authors consider that the central compartment in the Kangaroo is closed in the young form, and becomes open in Macropus just before the birth of the fomtus. In our specimen the central compartment was closed, and only communicated with the urogenital sinus by the two lateral passages, thus confirming the observation of these writers. 1 Proc. Zool. Soc., 1881, If. 976.