PHYSIOLOGY. 



C-19 



which I IK- logical value is that of negative evi- 

 dence, although in this case very strong. In re- 

 gard to In at, probably nothing further can be 

 brought fi'i-wanl. As to chemical change, how- 

 ever, it is possible that new and more delicate 

 methods may I Ting out. interesting results. Some- 

 thing alxi might be looked for from the histo- 

 logical comparison of exhausted and nonexhaust- 

 eil filters. A-suming, then, the practical inex- 

 haustibility of medullated nerve fibers, and the 

 slight, if any, chemical change during activity, 

 it remains to suggest a mode of transmission of 

 energy which shall be to a very slight extent in- 

 deed, if at all, other than a physical one. Of 

 such hypotheses the most fascinating one seems 

 that of Engelmann, who supposes the phenomena 

 of the nervous impulse to be an electrical one, 

 having a velocity in the internodal segments far 

 greater than the average velocity in the nerve, 

 the delay taking place at the nodes of Ranvier. 

 In support of this he maintains that the axis 

 cylinder is histologically discontinuous at the 

 nodes. This latter view is opposed by many 

 histologists, and Demoor maintains that the axis 

 cylinder, while continuous throughout, is of a 

 different constitution at the nodes. He consid- 

 ers that such a structure would fulfill the re- 

 quirements of the hypothesis of Engelmann. 

 This hypothesis Engelmann also holds to account 

 for the interruption of conductivity of the im- 

 pulse in a ligatured nerve. 



Although a large amount of work has been done 

 in the study of the nerves acting on the mam- 

 malian heart, the method of direct registration 

 of the movements of auricles and ventricles has 

 been used in only a few cases. To this fact are 

 probably largely owing the numerous gaps in our 

 Knowledge of the subject, as compared with the 

 exact knowledge we have of the actions of the 

 nerves in the cold-blooded animals. Having 

 shown in a former paper that the electrical 

 events accompanying the contraction of the 

 mammalian heart are exactly analogous to those 

 occurring in the frog and tortoise, W. M. Bayliss 

 and Krnest H. Starling instituted a new research 

 with a view to determining how far this analogy 

 extends to the innervation of the heart in those 

 two classes of animals, and especially with regard 

 to the influence of the two sets of cardiac nerves 

 on conduction between auricles and ventricles. 

 In their work the authors chiefly concerned 

 t hemsel ves with studying the conditions affecting 

 conduction from auricles to ventricles. Their 

 conclusion is that there is no essential difference 

 between the hearts of the mammals and of the 

 cold-blooded animals, and that each is subject to 

 the same varieties of nerve influence. 



The results of investigations undertaken by 

 Dr. Risien Russell to ascertain whether it is pos- 

 sible to separate the adductor fibers from the 

 abductor fibers of the recurrent laryngeal nerve, 

 show that these fibers are collected into several 

 separate bundles, each preserving an independ- 

 ent course through the nerve trunk to its ter- 

 mination in the muscle or muscles which it sup- 

 plies. It was also found that whereas in the 

 adult annual simultaneous excitation of all the 

 nerve fibers in the recurrent laryngeal nerve re- 

 sults in adduction of the vocal cord on the same 

 side, in the young animal the opposite effect 

 viz., abduction is that produced by an exactly 



similar procedure. When the abductor and ad- 

 ductor fibers are exposed to the air the abductor 

 nerves are found to lose their power of electrical 

 excitability much sooner than the adductors, 

 and this is true of both young and adult animals, 

 although in the former theadductor fibers retain 

 their excitability longer. It was further found 

 possible to separate the adductor fibers from the 

 abductor through the whole length of the recur- 

 rent laryngeal nerve to their termination in the 

 muscles, and also so accurately to separate the 

 two sets of fibers as to be able to produce abduc- 

 tion or adduction, as the case might be, without 

 evoking any contraction in the muscles of oppo- 

 site function. The complete separation of the 

 two functions was also shown by the degenera- 

 tion of the muscles related to one function 

 which followed the division of the correspond- 

 ing nerve fibers, while the muscles subserving 

 the other function remained unaffected. 



Experiments are described by Dr. Boruttau, of 

 Berlin, which were made to determine the cause 

 of the difference in latent period observed dur- 

 ing the direct and indirect stimulation of mus- 

 cles, it being greater in indirect stimulation. 

 The author had satisfied himself by a careful 

 repetition of the experiments under many vary- 

 ing conditions that the difference is due solely 

 to the resistance of the end plates. In connec- 

 tion with this paper, Prof. Gad pointed out the 

 possible bearing of the results obtained on the 

 processes which go on in other organs. Thus, re- 

 cent anatomical research has shown that in the 

 central nervous system there is no complete con- 

 tinuity between the axis cylinders and ganglia, 

 and hence the existence of- some intermediate 

 structure must be assumed, and a portion at 

 least of the slowing which impulses experience 

 in the central nervous system may be due to the 

 resistance offered by this structure. 



Some observations have been contributed and 

 an attempt has been made by Messrs. Jaffray 

 and Achard to reconcile the different theories 

 which have been held with reference to the oc- 

 currence of atrophy after hemiplegia. This 

 condition, according to Charcot and Leyden 

 and their followers, is a result of an affection of 

 the anterior horns in the spinal cord. Dejeriiu 1 , 

 on the other hand, ascribes the condition to an 

 affection of the peripheral nerves, while Quincke, 

 Eisenlohr, Babinski, and others hold that there 

 is no discoverable anatomical condition under- 

 lying the change, but that it is the result of a 

 functional disturbance in the cells. In two cases 

 examined by the authors, changes were found in 

 the anterior horn cells, so far confirming Char- 

 cot's views. To explain the different conditions 

 and reconcile the different theories, the authors 

 suppose that in the first place, on account of the 

 lesion of the pyramidal tracts, there is stimula- 

 tion of the cells of the anterior horns, giving 

 rise to contracture. If this stimulation is suc- 

 ceeded by exhaustion, then atrophy results, but 

 in this there are several changes. At first there 

 is simple muscular atrophy, the nerves not yet 

 being appreciably altered, and the anterior 

 horns and intramuscular endings being anatom- 

 ically intact. But later degeneration in the 

 motor nerves sets in, and in the peripheral end- 

 ings, and. last of all, the cells in the anterior 

 horns undergo visible atrophy. 



