THE PHYSIOLOGICAL CHEMISTRY OP NERVES. 535 



nodes of Eanvier as do stains, there only lies between it and 

 the axis-cylinder an extremely delicate layer of protoplasm, 

 Mauthner's sheath, which in no way would impede the en- 

 trance of the fluid into the axis-cylinder itself. 



The term "cylinder" suggests the tubular shape of the 

 latter: in accordance with Remak's view that it consists of a 

 delicate, longitudinally striated tube, filled with an albuminous 

 liquid. The prevailing view, however, is that of M. Schultz, 

 who considers the axis-cylinder as made up of fibrils united 

 by an intervening unknown substance. This seems to us to 

 vividly recall the arrangement of muscular fibers as regards 

 their relation with the blood-plasma: i.e., minute fibers into 

 which the plasma may freely enter. Again, we must not lose 

 sight of the fact, in this connection, that the axis-cylinder is 

 nothing but the elongated axon of a neuron, and that the 

 fibrilla3 now referred to, therefore, represent the intimate 

 structure of a neuron's axon. Now, as Schaf er holds that these 

 fibrillae are extremely fine tubes filled with fluid, and as the 

 character of this fluid is not known, we have good reason to 

 believe that they are channels for the blood-plasma: i.e., for 

 the oxidizing substance. 



But there is another feature which points to the axis- 

 cylinder as a channel for the oxidizing substance: i.e., the fact 

 that the so-called "medullary sheath" i.e., the myelin itself 

 contains a supposed "supporting frame-work." The strias rep- 

 resenting them were at first termed "clefts" or "incisures" by 

 Schmidt, Lautermann, and others, but Eanvier considered 

 them as protoplasmic septa which subdivide each internodular 

 segment of the nerve into several conico-cylindrical cham- 

 bers. W. H. Wynn, 32 who gives an excellent review of this 

 subject and the results of personal researches, refers to those 

 of Rezzonico 33 and Golgi, 8 * who "from the examination of fibers 

 treated by a mixture of bichromate of potash and osmic acid, 

 and afterward by nitrate of silver, find that each cleft is 

 occupied by what appears to be a thread of darkly-stained 

 substance passing spirally around the fiber. They consider," he 



88 W. H. Wynn: Journal of Anat. and Physiol., April, 1900. 

 "Rezzonico: Archivio per le Sci. med., Torino, vol. iv, 1880; and Gazzetta 

 med. ital. lomb., Milano, vol. i, 1879. 



8 * Golgi: Arch, per le Sci. med., Torino, vol. iv, 1880. 



