April 14, 1892] 



NATURE 



573 



SOCIETIES AND ACADEMIES. 

 London, 



Royal Society, March 31. — "The Abductor and Adductor 



Fibres of the Recurrent Laryngeal Nerve." By J. S. Risien 



; Russell, M.B., M.R.C.P. Communicated by Prof. V. Horsley, 



i F. R.S. (From the Pathological Laboratory of University 



College, London ) 



The first part of the following research consists in the separa- 

 tion and isolation of the different bundles of nerve fibres of 

 which the nerve trunk is composed, electrical exciiation of each 

 separate bundle, and ob ervation of the effects produced on the 

 vocal cords by such exciiation. 



Exposure of the different bundles of nerve fibres, under 

 exactly similar circumstances, to the drying influence of the 

 external air, with observation of the relative duration of vitality 

 possessed by the different bundles, forms the second part of the 

 investigation. 



Other methods were next instituted to control the results of 

 the foregoing, and the first of these, constituting the third 

 part of this work, consisted in tracing by post-mortem dissec- 

 tions each bundle of nerve fibres separated in the nerve trunk 

 to its termination in the mucous membrane or in a muscle of the 

 larynx. 



The next control method consisted in exposing the muscles of 

 the larynx immediately after death, and direct observation of 

 them during excitaiion of the separate bundles of nerve fibres, 

 this being controlled by occasional excitaiion of individual 

 muscles themselves. This forms the fourth part of the investi- 

 gation. The fifth or last part of the research served as a third 

 control method, and consisted in observations of the muscular 

 degenerations which followed division of one or other bundle of 

 nerve fibres in the nerve trunk, three weeks after such division. 



The results of these experiments show clearly : — 



(i) That the abductor and adductor fibres in the recurrent 

 laryngeal nerve are collected into several bundles, the one dis- 

 tinct from the other, and each preserving an independent course 

 throughout the nerve trunk to its termination in the muscle or 

 muscles which it supplies with motor innervation, a condition of 

 things, the possibility of which was suggested by Dr. Semon 

 more than ten years ago. from the evidence of pathological facts. 



{z\ That while in the adult animal simultaneous excitation of 

 all the nerve fibres in the recurrent laryngeal nerve results in 

 adduction of the vocal cord on the same side, abduction is the 

 effect produced in a young animal by amexactly similar procedure. 



(3) That when the abductor and adductor fibres are exposed to 

 the drying influence of the air under exactly similar circumstances, 

 the abductors lo-e their power of conducting electrical impulses 

 very much more rapidly than theadduct rs — in other words, they 

 are more prone to succumb than are the adductors — a fact which 

 has for 1 )ng been recognized and insisted on by Dr. Semon as 

 being the case in the human subject, and in support of the truth 

 of which that observer has adduced so many powerful arguments. 



(4) That, even in he young dog, the abductor nerve fibres, 

 though perserving their vitality much longer than in the case of 

 the adult animal, nevertheless in the end succumb before the 

 adductor fibres. 



(5) That this death commences at the point of section of the 

 nerve, and proceeds gradually to its peripheral termination, and 

 does not take place in the whole length of the nerve simul- 

 taneously. 



(6) That it is possible to trace anatomically the abductor and 

 adductor fibres throughout the whole length of the recurrent 

 laryngeal nerve to their termination in the one or other group of 

 larynt»eal muscles, and that these fibres appear to bear a fixed 

 relationship to each other throughout their course, the abductors 

 being situated on the inner side of the nerve or that next to the 

 trachea, while the adductors are on the outer side. 



(7) That it is possible to so accurately separate these two sets 

 of fibres in the nerve trunk that excitation of either of them 

 evokes contraction of the abductor or adductor muscles, as the 

 case may be, without evoking any contraction whatever in the 

 muscle or muscles of opposite function 



(8) That the bundle of nerve fibres concerned with one func- 

 tion may be divided without injury to that concerned with the 

 opposite function, and that such division is followed by atrophy 

 and degeneration of the muscles related to that function without 

 any such changes being detectable in the muscles related to the 

 opposite function. 



Further, it is clear that the theory advanced by Mackenzie, 

 and which has since found favour with many, viz. that p )ssibly 



NO. I 172, VOL. 45] 



the reason why the abductor fibres succumb before the adductor 

 in affections of the nerve is because they are more superficially 

 and circumferentially arranged, while the adductor fibres are 

 situated deep in the substance of the nerve, is shown by these 

 experiments to be entirely erroneous. 



One point which is difficult to explain is why there should be 

 so marked a difference between the recurrent laryngeal nerve of 

 a young and that of an adult dog, as regards the respective pre- 

 dominance of abductor or adductor representation in the trunk 

 of the nerve. Possibly the reason why the abductor influence 

 is in the ascendency in the young dog is because the power of 

 phonation is still imperfectly developed, and with it both the 

 muscle and nerve fibres subserving this function are also imper- 

 fectly developed, while the function of respiration is from the 

 beginninif fully developed, and with it the muscle and nerve 

 fibres connected with that function. That the reverse should be 

 the case in the adult animal may well be due to the fact that 

 phonation is perfectly developed, while respiration has become so 

 automatic that very feeble stimuli are necessary to keep it going. 



" Interference with Icterus in Occluded Ductus Choledochus." 

 By Vaughan Harley, M. D. 



This paper is one of considerable biological-pathological 

 interest, as it gives an experimental explanation of the strange 

 discovery made by Kufferath, in 1880, that by placing a ligature 

 on the thoracic-duct, the jaundice-producing effects of an occlu- • 

 sion of the common bile-duct could be instantly arrested — which 

 fact Kufferath did not so much as even attempt to explain ; and 

 no other physiologist having either confirmed or negatived the 

 statement, far less offered any explanation of it, there were 

 two problems requiring to be solved when Dr. Vaughan Harley 

 entered upon the investigation : — 



(i) Does ligaturing the thoracic duct actually prevent the 

 jaundice which otherwise inevitably occurs after occlusion of the 

 common bile-duct ? 



(2) If it does, how can such a remarkable phenomenon be 

 explained ? seeing that the chyle-transmitting thoracic duct 

 has no apparent physiological connection with the ductus 

 choledochus. 



Kufferath only kept the animals he operated upon alive from 

 I to 2\ hours — a period of time far too short to admit of any 

 impor ant morphological changes occurring, which could yield 

 a clue to the mystery. Hence the first thing was to try and 

 find a means of keeping the animals experimented upon alive 

 for much longer periods of time, after both ducts had been 

 ligatured. This was successfully done by feeding the dogs on 

 fat- free food, containing only small proportions of proteids. It 

 was found that when so fed dogs could not only be kept 

 alive for weeks, but even months ; and, what was stranger still, 

 they even gained in weight. 



The non-appearance of jaundice after ligature of the bile-duct 

 when the chyle-duct was also tied, appeared remarkable from 

 the fact that it was by all believed that both bile pigments and 

 bile acids were always absorbed by the bl )od capillaries from 

 the bile ducts ; whereas it is now shown experimentally, in 

 this paper by Dr. Vaughan Harley, that the blood capillaries 

 have absolutely nothing whatever to do in the matter, and that, 

 contrary to what has been up till now imagined, the pent-up 

 bile is solely absorbed from the bile-ducts by lymphatics, and 

 carried by them into the general circulation by the circuitous 

 route of the thoracic duct. 



Dr. Vanghan Harley has further demonstrated experimentally 

 that, if a sufficient length of time is allowed to elapse after 

 ligaturing the thoracic duct, bile pigment and bile acid again 

 appear in the urine just as if the thoracic duct had not been 

 ligatured at all, and that this arises from the fact that collateral 

 lymphatics shoot out from the thoracic duct at a point below 

 the ligature, and convey its contents into the right innominate 

 vein. Hence he says that the three following conclusions may be 

 drawn from the results obtained from his experiments : — 



(i) That bile existing in the bile-ducts can only reach the 

 blood through the intervention of the lymphatics, 



(2) Seeing that lymphatics surround the liver blood-vessels, 

 one is forced to believe that bile pigment and bile acid cannot 

 pass through the endothelium of the blood capillaries in the 

 liver ; or, perhaps, even throughout the body. The fact 

 that bile reaches the blood when it has escaped into the peri- 

 toneal cavity is no argument against this view. For in that case 

 it reaches the blood through the lympha'ics of the diaphragm, 



(3) After the left thoracic duct of the dog has been ligatured 

 for some time, collateral lymphatics are opened up or developed 

 from it leading into the right innominate vein. 



