Literary Notices. , xxvii 



centre with distributing tracts. As a result of each molecular disturb- 

 ance, the end cells suffer a change in the processes of metabolism, which 

 change will vary with the nature of the cells (tendon, muscle, etc ). The 

 nutritive processes are there influenced through the more elementar^^ 

 metabolic processes. Every nerve, and especially everv centrifugal 

 nerve, is therefore a trophic nerve. The various processes governed by 

 these nerves (secretion, contraction, etc.) are simply the results of the 

 trophic intiuence. 



For example, the young muscle cell contains an irregularly 

 arranged mass of granules, which gradually arrange themselves into 

 the transverse bars so characteristic of voluntary muscle. This struc- 

 ture is the result of the oft-repeated contraction. It has been observed 

 that, in contraction, the elementary granules enlarge, and their combined 

 increase causes the increase in diameter of the Bowman's discs or dark 

 stripes. The author regards the only satisfactory explanation to be an 

 increased absorption of tluid from the light portion of the fibre, which 

 absorption is the result of altered molecular conditions or a form of 

 metabolism brought about in the granules by the nerve stimulus. In a 

 similar way the centripetal nerve gives rise to sensation simply because 

 its stimulus alters the vital activity of its central terminal cell. 



Thus there are no special trophic nerves because every nerve is 

 trophic. The distinction between sensory and motor nerves, while 

 useful for c nvenience sake, is more accurately expressed by centripetal 

 and centrifugal. 



Degeneration and Atrophy as a Result of Section of the 

 Cranial Nerves. (') 



This exceedingly interesting paper affords a brief historical review 

 of the development of the v, Guddcn-Waller method of experiment. 

 Mayser, Ganser, von Gudden and the author had been associated for a 

 number of years in this difficult department, with results which certainly 

 substantiate the author's claim for it. Two classes of experiments are 

 chiefly relied upon: 



1. A cell group is extirpated in a young animal. When adult the 

 associated fibres are atrophied, enabling one to trace the course of the 

 tract in question in detail. In this way, after injury to the Gasser's 

 ganglion, the author demonstrated the loss of the fibre branches in the 

 substantia gelatinosa of the tuberculum Rolandi, and Monakow found 

 similar result in the corpus geniculatinn externum after enucleation of 

 the eye, while Gudden determined that the pyramid fibres pass directly 

 into the cord by extirpation of motor areas, 



2. A nerve root or fibre system is sectioned in a young animal, and, 



I FoKEL, Alg . " Ueber das Verhaltniss der experimentallen Atrophic und Degen- 

 erations methode zur Anatomic und Histologic des Centralnervensystem," Festschrift 

 zur Feier des f iinfzig-jahrigen Doctor-Jubilaums der Herren Prof. Dr. Karl Wilhelin von 

 Nageli und Prof. Dr. Albert von KoUiker, Zurich, 1891. 



