114 THE PHYSIOLOGY OF NERVE 



swelling at the junction of the axis-cylinder with the substance of the muscle-fiber. 

 At this point the former loses its medullary sheath as well as the neurolemma, these 

 envelopes becoming continuous with the sarcolemma of the muscle fiber. The 

 plates themselves appear to be made up of fibrillar arborizations and possess a 

 faintly granular or cloudy appearance. At the point of contact with the myo- 

 plasm, the arborization is more dense and presents a coarse granular appearance, 

 forming what is known as the sole or bed of the end-plate. 



The Chemistry of Nerves. — The composition of nerves has not 

 been studied in great detail. Whatever data we possess have been 

 derived very largely from analyses of the white matter of the cerebrum 

 which, of course, is composed almost exclusively of nerve-fibers. 



Fig. 66. — End-plates; Chlorid of Gold Preparation to Show the Axis Cylin- 

 ders AND Their Final Ramifications of FibrilluE. X 170. (Szymonowicz.) 



The proteins are abundant and especially so in the axis-cylinder. One of these 

 is a nucleoprotein which coagulates at 56 to 60° C. There are also present certain 

 globulins. One of these coagulates at 47° C. and the other at 70 to 75° C. Accord- 

 ing to Halliburton,^ the sciatic nerve is made up of 65.1 per cent, of water and 

 34.9 per cent, of solids of which the proteins furnish 29.0 per cent. The nerves of 

 the cold-blooded animals begin to lose their irritability at about 40° C. and shorten 

 more and more as the temperature rises. 



The lipoids are also very abundant. They comprise phosphatides, such as 

 lecithin and kephalin, galactosids and cholesterin or cholesterol in the following 

 proportion: 2 



Medullated Non-medullated 



nerve nerve 



Cholesterin 25.0 47.0 



Lecithin 2.9 9.8 



Kephalin 12.4 23.7 



Galactosids 18.2 6.0 



1 Arch, of Neurology, ii, 1903, 727. 



2 Falk, Bioch. Zeitschr., xiii, 1908, 153; and Bang, Ergebn. der Physiol., vi, 

 1907, 131. 



