in 



: 



ANATOMY AND PHYSIOLOGY OK THE NERVOUS SYSTEM. G07 



2. Protagon. Dr. W. J. Gies has shown that protagon is 

 not a true body but a mixture of substances.. 



3. Kephalins. 



(e) Cerebrins (nitrogenized substances, or 



Cerebrosides. The name cerebrosides indicates that they are 

 glucosides, and that the sugar (cerebrose) obtained from 

 them has been identified as galactose. 



(f) Cholesterin. 



(g) Extractives : creatin, xanthin, hypoxanthin, inosite, lactic 



acid, uric acid, and urea, 

 (h) Gelatin, 

 (i) Inorganic salts, of which the alkaline phosphates and 



chlorides are the most abundant. 



Haitai has shown that lecithin, when administered to white rats, 

 caused a gain of 60 per cent, in body-weight compared with the nor- 

 mal animal. Hence lecithin is a stimulant of normal growth. 



KEACTION. When passive, nerve-tissue is neutral or feebly alka- 

 line. When active or dead it is said to be acid. 



It is found that after death nerves have a more solid consistence. 

 Probably some coagulation occurs which is to be compared to the 

 stiffening of muscle. Simultaneously there is generated and liberated 

 a free acid. 



Mechanical Properties. A remarkable property of nerve-fibers 

 is the absence of elastic tension according to the varying positions of 

 the body. Divided nerves do not retract. 



The cohesion of a nerve is an important property. Oftentimes 

 hen a limb is forcibly torn from the body the nerve still remains 

 tact (though considerably stretched), while the other soft tissues 

 re completely severed. The sciatic nerve at the level of the popliteal 

 space requires a force equal to one hundred and ten or one hundred 

 d twelve pounds to rupture it; the median or ulnar require forces 

 ual to forty or fifty pounds. The latter nerves will stretch six or 

 ght inches before the point of rupture is reached. It is upon the 

 owledge of this fact that the method of nerve-stretcliing is employed 

 some forms of neuralgia. 



Nerve-metabolism. Some extractives are obtained which are 

 lieved to be decomposition products of the nerve. 



The Nerve-centers. The nerve-fibers and nerve-cells comprise 

 e essentials from which the nerve-centers are formed; the elements 

 ust, of course, be held together by enveloping neuroglia. The term 

 ter is merely applied to an aggregation of nerve-cells which are 



