164 STRUCTURE OF THE NERVOUS SYSTEM, BY MAX SCHULTZE. 



from a single trunk fibre, as was first observed by Rud. Wagner 

 in the nerves of the electric organ of the Torpedo * By far the 

 most remarkable example of nerve division occurs, however, in 

 the electric eel (Malapterurus electricus). Here, according to 

 Bilharz, each of the two electric organs which lie like masses 

 of bacon-fat beneath the skin, receives a nerve from the medulla 

 oblongata, consisting of only a single medullated fibre, having 

 a diameter- of 0'025 millimeters,*)* which, in order that it may 

 give a peripheric terminal fibre to each electrical plate, must 

 divide millions of times. 



The sheath of Schwann disappears sooner or later in the 

 process of division, and is consequently absent in the ultimate 

 fibrils, as may be seen, for example, in the nerves of the cornea. 

 Here the medulla also sooner or later disappears from the sur- 

 face of the axis cylinder. Coincidently, or somewhat later, the 

 sheath of Schwann can no longer be distinguished, the axis 

 cylinder, which alone remains, repeatedly divides, and the fine 

 primitive fibrillae, as first demonstrated by HoyerJ and Cohn- 

 heim, ultimately project from the sub-epithelial tissue between 

 the cells of the tesselated epithelial layer of the conjunctiva 

 corneae, and terminate by free extremities at the surface. The 

 same appearance may be seen in many other nerves, as in the 

 acoustic and optic, in the nerves of the tongue, in those dis- 

 tributed to the glands and elsewhere, though in these instances 

 each primitive fibril is connected with a peculiar terminal 

 apparatus, which will be hereafter described. In many parts, 

 however, the division into primitive fibrils does not take place ; 

 that is to say, an axis cylinder of appreciable diameter termi- 

 nates, so far as we at present know, without previously breaking 

 up into the finest nerve filaments. The above-mentioned 

 examples, the nerves distributed to many electrical organs, to 

 the transversely striated muscles, the Vater's (Pacini's) cor- 



* Feiner Bau der JElekt. Organes im Zitterrochen, " Minute Anatomy of 

 the Electric Organs of the Torpedo/' 1847, p. 17. 



t According to Bilharz, loc. cit., p, 22 ^Qi". 



| Uber die Endigungen der sensibeln Nerven in der Hornhaut, Virchow's 

 Archiv, Band xxxviii., 1867, p. 343. 



Reichert and Du Bois Raymonds' Archiv, 1866, p. 180. 



