THE MAIN PERIPHERAL CONNECTIONS OF THE HUMAN SYMPATHETIC NERVOUS SYSTEM By T. K. POTTS, M.B., CH.M. (SYDNEY)1 BIIE recent investigation (5,7) of the functional significance of the sympathetic system by 1)r N. D). itoyle and Professor J. I. Hunter has revealed the necessity for a re-examination of the anatomy of the human sympathetic system. Ini particular the operations of ramisectioni (7, 8) devised by Dr Royle, in collabora- tion with Professor Hunter, call for a more exact determination of the precise position and topographical relations of the sympathetic cord and its ram? cotitnunicantes than at present is available. The dissection described ill this note was undertaken primarily to provide the surgeon with this guidance. In this matter, two regions stand out as having assumed an added interest ill the light of recent research. I refer to those regions associated with the operations known as cervical, and lumbar sympathetic ramisection, which are performed to remove the rigidity of the musculature of the extremities ill spastic paralysis (2,3,4,5, 7, 8, 9,10). As a description of the rari commnunicantes necessarily involves some mention of the arrangement of corresponding ganglia, this will be done in considering the various regions. To facilitate demonstration, the services of Miss D. Harrison were procured and, under my guidance, faithful repro- dluetions of the dissection were made by her. The dissection has been mounted, and placed in the Wilson. Museum of Anatomy, at the Medical School, Uni- versity of Sydney. The cervical portion of the sympathetic is characterized by the absence of segmental ganglia, and of white rami comnimunicantes. Two constant ganglia are found-the superior and inferior cervical ganglia-and a variable middle cervical ganglion, variable in that it may be absent; and, whehn present in its usual position, lying commonly about the levelof the inferior thyroid artery, i.e. the level of the 6th cervical vertebra; or else lying in close proximity to the inferior cervical ganglion. When this latter arrangement is found, the two ganglia are commonly united by stout cords embracing the vertebral artery. The absence, or the position when present, of this middle ganglion, affects the arrangement of the grey rami to the 5th and 6th; or 4th, 5th, 6th and 7th cervical nerves. The superior cervical ganglion is usually placed at the level of the 2nd and 3rd cervical vertebrae, and under cover of the posterior belly of the digastric muscle, or a little above that level. This ganglioni furnishes grey rami to the 1st, 2nid and 3rd, and, sometimes also, the 4th cervical nerves; in this specimen. 1 From the Department of Anatomy, University of Sydney. Anatomy LIX '3 130 T. K. Potts to the 1st, 2nd and 3rd only. The 1st cervical nerve is not shown in the diagram (vide Pls. 1 and 6). These rami lie in the region of the lateral border of the longus eapitis muscle, and join the nerve, as a rule, as it lies in the groove of the transverse process of the vertebra, or as it emerges from the groove be- tweeni the anterior and posterior tubercles of the transverse processes. Further- iiore, the ramus joins the nerve on the anterior, or antero-iinferior aspect of the nerve. I have not seen an instance of a ramus junctioning with a spinal nerve on the posterior aspect of the latter. The middle cervical ganglion, when situated about the level of the 6th cervical vertebra, usually supplies rami to the 5th and 6th cervical nerves; at times, also, to the 4th and 7th. When this ganglion is absent, or lies in close proximity to the inferior cervical ganglion, these cervical nerves, the 5th and 6th, and possibly also the 4th and 7th, usually derive their rami direct from the sympathetic trunk (PI. 1); and it is my experience that this middle ganglion, when lying adjacent to the inferior ganglion, plays a subsidiary role from the point of view of furnishing rami to the cervical nerves. In this specimen only one ramus, viz. one to the 8th nerve on the right side, arose from this ganglion; but the ganglion contributes largely to the cardiac plexuses -especially on the left side (PI. 1). Here I would draw attention to two rami (PI. 1) arising from the symi- 1athetic trunk about the level of the anterior tubercle of the transverse process of the 6th cervical vertebra. They run a more or less parallel course, cranially and medially, pierce the longus colli muscle, and then pass directly backwards in the interval between the transverse processes of two adjacent vertebrae; and, in this case, the upper ramus is associated with the 5th cervical nerve, and the lower with the 6th. Both these rami effect junction with the nerves as the latter lie in the grooves of the transverse processes of corresponding vertebrae. At first I thought these rami were muscular twigs to the longus colli muscle; but subsequent dissection revealed the facts as stated. In addi- tion, both rami give twigs to the vertebral artery. The inferior cervical ganglion is commonly situated in the region of the level of the neck of the first rib, but may occupy a slightly lower level. The ganglion supplies rami to the 7th and 8th cervical, and ist thoracic nerves (Pls. 2 and 7). A single ganglion may supply two or more spinal nerves, or two ganglia may supply a single spinal nerve; and here is an excellent illustration of the former. A rams ascends in front of a spinal nerve, or nerves, if that ramus is associated with a nerve at a higher level. For example, it passes in front of the 8th and 7th if ascending to the 6th cervical nerve, and does not pass behind the nerve or nerves. A ramus in this region measures, as a rule, from *5 mm. to 1*5 mm. across. The scalenus anterior mnusclc presents an important relation to the grey rami in this region. The 5th and 6th or 7th nerves may lie in front of this muscle, may pierce the niuscle, or may lie under cover of the ninscle. So that in some cases iii which these nerves lie upon, or pierce this muscle, it is not Connections of thef Sympathetic 131 tlncomnl1oln to find all the ramii, or sonic of theni, lying upon the surface of the muscle, or wandering among its fibres. In the supposedly normal type, when these cerv-ical nerves lie behind the muscle, the rami may lie upon, or pierce the muscle. The inferior cervical ganglion is here shown as supplying one grey ranmus to the 6th cervical nerve, two to the 7th, three to the 8th, and one to the 1st thoracic nerve, i.e. seven. There are still others requiring mention. I wish to draw attention to two or three rami on this specimen which lie to the medial side of the vertebral artery in a triangle formed by the upper border of the neck of the first rib below, by the lateral margin of the longus colli muscle mcdially, and by the medial border of the vertebral artery laterally. The shorter and more medially placed is a large ramus (which may be double) lying almost under cover of the lateral border of the longus colli muscle (PIs. 1, 2 and 7). It joins the 8th cervical nerve under cover of the muscle. The other rams, single on the left side, double on the right, lies to the outer side of the last-mentioned ramus; and, taking the medial border of the vertebral artery as its guide, ascends upwards, and medially. This ramus appears to be fairly constant. It was present in the same position as a single trunk on the left side, and as a double trunk on the right in this specimen; and as a single trunk it was present on both sides of a full-term foetus; and also in a dissection of another adult cadaver. On only one occasion was it a double trunk. In every instance its main association is with the 7th cervical nerve; the greater pro- portioll of its fibres turningldistally at its point of junction with the nerve, while the nerve lies in the groove between the 6th and 7th cervical vertebrae. A fine branch is also continued upwards to the 6th cervical nerve; and in one case was followed on to the 5th nerve. At first I regarded this rams as the vertebral plexus, aggregated into a single or double trunk at its commence- ment; but subsequent dissection has convinced me that it is a grey rams associated mainly with the 7th cervical nerve. To sunmmarisc, then, I have found three rami to the 5th cervical nerve; three to the 6th; three to the 7th, and three to the 8th; so these cervical nerves, 5th, 6th, 7th and 8th, may derive their rami from three sources, viz. from the sympathetic trunk; from the middle cervical ganglion (whatever its position when present); from the inferior cervical ganglion. In addition to these, Spalteholzli) mentions branches from the vertebral plexus to these cervical nerves. The first white rams, which is associated with the 1st thoracic nerve, connects this nerve to the inferior cervical ganglion, or to the 1st or 2nd thoracic ganglion. This white rams is larger and whiter than the corre- sponding grey ramnus, and lies lateral to, or lateral and posterior to the grey ramus, and is directed from above downwards and medially (Pls. 6 and 7). This white ramnus must be left intact in the operation of cervical ramisection if papillary effects are to be avoided.