ON THE LARGER MEDULLATED FIBRES OF THE SYMPATHETIC SYSTEM. BY J. N. LANGLEY, M.A., F.R.S., Fellow and Lecturer of Trinity College, Cambridge. A SHORT time ago, in a Paper chiefly devoted to the spinal origin of the upper part of the sympathetic system, I' had occasion to consider the general histological characters of the system. At about the same time, and independently, a Paper by Mr Edge- worth' appeared in this Journal, also dealing with the histological characters of the sympathetic system, but giving an account completely at variance in nearly all essential points to that given by me. I have in consequence felt it necessary to repeat many of my obser- vations'. The results do not differ from those I have previously published, and I do not propose to re-state them here. But it seems to me un- advisable to allow Mr Edgeworth's account to pass without comment. 1. In the sympathetic system of the dog, Mr Edgeworth describes, in accordance with previous accounts, medullated fibres 1P8 to 3-6 , in diameter, and medullated fibres 7 2,u to 9,u in diameter. The latter, he calls, 'large sympathetic fibres.' He nowhere mentions that there are sympathetic fibres of inter- mediate diameter and the whole tenour of his paper is that such fibres do not exist. In fact, fibres of intermediate diameter occur in nearly all parts of the syinpathetic system, and at some places in considerable numbers. 2. Mr Edgeworth describes in the vagus at the diaphragm, medul- lated fibres of 4-5 to 6-3 ,u in diameter, and so far correctly. But when

1 "On the Origin from the Spinal Cord of the Cervical and Upper Thoracic Sympathetic Fibres with some Observations on White and Grey Rami Communicantes." Phil. Trans. Roy. Soc., B. p. 85, 1892. 2 "On a Large-Fibred Sensory Supply of the Thoracic and Abdominal Viscera." This Journal, Vol. xiii., May, 1892, p. 260. 3 All the histological points I mention here I have repeated on the nerves of the dog since the publication of Mr Edgeworth's Paper. The nerves were treated with osmic acid 1 p.c. and teased out. ON LARGE SYMPATHETIC FIBRES. 787' he meets fibres of this diameter-which he calls large vagus fibres-in the peripheral parts of the sympathetic system, he assumes that they are vagus fibres. This assumption is unfounded, since medullated fibres of 4 5 to 6-3 , in diameter are present in the sympathetic in situations where there can be no question of any admixture of vagus fibres. 3. Mr Edgeworth states that no 'large sympathetic fibres' are present above the 1st thoracic ramus communicans, nor any below the 3rd lumbar ramus communicans. I cannot agree with either of these statements. I have always found somle such large medullated fibres (i.e. 7-2 A or upwards) in the grey rami ofthe lower cervical nerves; in the white and in the grey ramus of the 4th lumbar nerve, and in the grey rami of the 5th, 6th and 7th lumbar nerves. The 'large' medullated fibres may be few, but they' are not absent, and with them are a con- siderable number of fibres of about 5 , in diameter, (10 to 30 in a ramus). To the sacral rami I have paid less attention, but I have found large medullated fibres in the 1st sacral ramus. 4. Mr Edgeworth states that no 'large sympathetic fibres' occur in the sympathetic chain below the 6th lumbar grey ramus. I have found them in the upper sacral region; how much farther down they occur I have not determined. 5. Mr Edgeworth states that the hypogastric nerve "is found to consist of grey fibres, small medullated fibres and large sympathetic fibres-no large vagus fibres being present." Curiously enough the hypogastric of the dog is a nerve in which the fibres of the size of ' large vagus fibres' are abundant, whilst fibres of greater diameter than 7-2 , are rare. 6. Mr Edgeworth gives one observation from the cat, he says the average size of the large medullated fibres in the of the cat is 6 3 IA. I find that the splanchnic of the cat-as that of the dog-is par- ticularly well supplied with fibres of the 7-2 A to 9,0 class. 7. The diagram given by Mr Edgeworth (Plate X. op. cit.) besides embodying the points I have already mentioned, contains"other represen- tations which seem to me misleading. The inferior mesenteric is represented as receiving its large sympathetic fibres almost entirely from the minor splanchnic nerve. I find that it receives few if any such fibres from this source. The nervus dorsalis penis is represented as arising from the hypo- gastric plexus, into which the hypogastric nerve runs. In point of fact, 788 J. N. LANGLEY. the nervus dorsalis penis does not touch the hypogastric plexus. It arises it is true from certain spinal nerves, which send branches to the hypogastric plexus, but the plexus lies by the side of the rectum, about an inch distant from any part of the nervus dorsalis penis. 8. There are three points which I think ought not to be passed unnoticed. Mr Edgeworth assumes that all the large medullated fibres which occur in the white and grey rami communicantes have just issued from the cord and are on their way to the sympathetic system. This view has no evidence, worth the name, in its favour, and I have in the Paper quoted above endeavoured to shew that it is incorrect. Mr Edgeworth states by implication that the 3rd lumbar nerve is the lowest nerve which supplies motor fibres to the viscera by way of the sympathetic. In fact, the 4th lumbar nerve normally, and the ath lumbar nerve occasionally sends such fibres to the sympathetic. He also states by implication that the efferent inhibitory fibres have no connection with 'lateral' or with 'collateral' ganglia. I have brought forward evidence that (to take one or two instances only) inhibitory vascular fibres for the fore and hind limb are connected with 'lateral' ganglia, and that the sympathetic inhibitory fibres to the intestine are connected with 'collateral' ganglia.