376 THE NERVE-TISSUE. 



The precipitate B is placed in ether. This dissolves the greater 

 portion, while a smaller amount remains uudissolved. The latter 

 consists of protagon, which was previously held in solution, owing 

 to the presence of cholesterin. The soluble portion is treated with 

 alcohol so long as a precipitate forms. This precipitate we term C, 

 and the alcoholic filtrate I). If a specimen of D is treated with an 

 alcoholic solution of platinum chloride, a precipitate results ; this 

 is not abundant, however, and consists of a chloroplatinate of leci- 

 thin. To isolate the lecithins as such, the alcoholic solution is pre- 

 cipitated with acetone, or the ether-alcohol is distilled off, when the 

 lecithins remain as a tough, wax-like mass. 



Of the nature of the substance or substances which are contained 

 in the precipitate C, nothing definite is known. Ziilzer apparently 

 was able to isolate one of these, however, and found it to contain 

 both nitrogen and phosphorus. He suggests that it may possibly 

 belong to the so-called cephalins of Thudichum. But of the nature 

 of these also our knowledge is as yet insufficient to warrant their 

 description at this place. 



The Cholesterins. Cholesterin s are found in nerve-tissue, both 

 in the free state, and as so-called combined cholesterins, but of the 

 chemical character of the latter we are as yet in ignorance (see 

 p. 67). _ 



The isolation of free cholesterin has been described above. 



The Extractives. The extractives of nerve-tissue, as I have 

 already stated, are essentially the same as those which can be 

 isolated from other organs of the body. They comprise traces of 

 kreatin, uric acid, xanthin, hypoxanthin, guanin, adenin, inosit, 

 volatile fatty acids (acetic acid and formic acid), lactic acid, glycogen, 

 leucin (or rather a lower member of the homologous series 

 C 2n H-2n + iNO 2 ), and urea. In addition, jecorin, cholin, and neu- 

 ridin have also been found ; neurin, on the other hand, does not 

 occur in the brain under normal conditions. 



Neuridin is of special interest, as the substance is constantly 

 formed during the putrefaction of meat and gelatin, and has also 

 been obtained from cultures of the typhoid organism. According 

 to Brieger, who first isolated the body, it is also present in traces in 

 the yolk of birds 7 eggs. It is a diamin of the composition C 5 H 14 N 2 . 

 With the chlorides of gold and platinum it forms well-defined 

 crystalline salts. On boiling with caustic alkalies it is decomposed 

 into trimethyl-amin and dimethyl-amin. It is not toxic. 



Jecorin is a substance of unknown composition, but apparently 

 contains both sulphur and phosphorus. It is not exclusively encoun- 

 tered in nerve-tissue, but has also been found in traces in the liver, in 

 the muscles, and, according to some observers, in the blood. It 

 reduces cupric oxide in alkaline solution on boiling, and on cool- 

 ing separates out in the form of a thick jelly. It is soluble in ether, 

 and can be precipitated from its solutions by alcohol* 



