32 NERVOUS TISSUE. 



When the aqueous extract of muscle from which the creatin has been crys- 

 tallized out (see Creatin) is precipitated by neutral lead acetate, a filtrate is 

 obtained from which inosite is precipitated by the addition of the basic acetate 

 test. It crystallizes from its solution in alcohol in rhombic plates or prisms 

 represented by the formula C 6 H 12 O 6 + 2H 2 O. 



Creatin (C 4 II 9 N 3 O 3 ) is obtained by direct crystallization from the water- 

 extract of meat. To prepare it, the extract must be first freed from albumin 

 by boiling, after which the phosphates and sulphates must be precipitated 

 by adding to the strained liquid a mixture of baryta water and baric nitrate. 

 The liquid having been filtered, the filtrate is evaporated over a water-bath 

 to a small bulk, when creatin separates in hard brilliant crystals. Creatin, 

 when treated with boiling solution of baryta, splits into Sarkosin (Methyl- 

 glycin) and Urea (C 4 H 9 N 3 O 2 + H 2 O = C 3 H 7 NO 2 -f CO (NH 2 ) 2 ). 

 When heated with acids, it loses water, and is converted into Creatinin 

 (C 4 H 7 N 3 O). 



Hypoxanthin (C 5 H 4 N 4 O) (Sarkin of Strecker), occurs in the tissue of 

 the spleen and in muscle. It exists in the mother liquor of creatin, and can 

 be precipitated from it as an impure compound of argentic nitrate and 

 hypoxanthin by treating the extract with solution of nitrate of silver rendered 

 slightly alkaline by ammonia. Hypoxanthin, like xanthin, is soluble in 

 nitric and hydrochloric acids yielding crystalline compounds. Heated and 

 evaporated with fuming nitric acid, it gives the same yellow residue as 

 xanthin. 



Xanthin (C 5 H 4 N 4 O 3 ) the xanthic oxide of Prout, exists in extremely 

 small quantity in urine, in the tissues of certain organs, and as an occasional 

 constituent of calculi. It is very insoluble in water, but soluble in hydro- 

 chloric and nitric acids, giving crystallizable compounds with both. When it 

 is heated with fuming nitric acid, and the product evaporated to dryness, 

 a pale yellow patch is left ; from this circumstance it derives its name. 

 Xanthin can be prepared artificially by the action of oxidizing agents on 

 Hypoxanthin. 



NERVOUS TISSUE. 



Of the proteids of the brain little is known. The grey 

 substance is said to be acid, even when perfectly fresh. 

 All nervous tissue contains, in addition to Cholesterin and 

 Lecithin, which exist everywhere, a body called Cerebrin, 

 which is peculiar to the nerve fibres. 



CRYSTALLINE PRODUCTS of the alcohol-ether extract of BRAIN. 



Neurin or Cholin (N (C H 3 ) 3 (C 2 H 5 O) OH) is a strongly basic, colourless 

 syrupy fluid, which forms crystalline salts with acids. It is soluble in alcohol 

 and water, not' in ether. It is readily decomposed by heat, yielding trimethy- 

 lamine, ethylene oxide, glycol (C 2 H 4 (HO) 2 ) and water. It is obtained by 



