MUSCLE. 257 



taurin in cephalopoda ; glycocoll in mollusks, pecteii irradians ; and creatinin 

 in luvarus imperialis, etc., etc. 



The xanthin bodies, with the exception of carnin, have been 

 treated on pages 47-52, and therefore among the extractive bodies 

 we will first consider the discussion of creatin. 



Creatin, C 4 H 9 N 3 2 -\- H 2 or METHYLGUANIDIN-ACETIC ACID, 

 NH:C(NH 2 ).N(CH 3 ).CH 2 .COOH + H 2 0, occurs in the muscles of 

 vertebrate animals in variable amounts in different species ; the 

 largest amount is found in birds. It is also found in the braia, 

 blood, transudations, and the amniotic fluid. Creatin may be pre- 

 pared synthetically from cyanamid and sarcosine (methylglycocoll). 

 On boiling with baryta-water it decomposes, with the addition of 

 water, and yields urea, sarcosine, and certain other products. Be- 

 cause of this behavior several investigators consider creatin as a 

 step in the formation of urea in the organism. On boiling with 

 acids creatin is easily converted, with the elimination of water, into 

 creatinin, whicli occurs in urine, and which has also been found in 

 the muscles of the dog by MOKARI (see Chapter XIV). 



Creatm crystallizes in hard, colorless, monoclinic prisms which 

 lose their water of crystallization at 100 C. It dissolves in 74 

 parts of water at the ordinary temperature and 9410 parts abso- 

 lute alcohol. It dissolves more easily with the aid of heat. Its 

 watery solution has a neutral reaction. Creatin is not dissolved by 

 ether. If a creatin solution is boiled with precipitated mercuric 

 oxide, this is reduced to mercury and oxalic acid, and the disgust- 

 ing-smelling methyluramin (methylguanidin) is developed. A 

 solution of creatin in water is not precipitated by basic-lead acetate 

 but gives a white, flaky precipitate with mercurous nitrate. When 

 boiled for an hour with dilute hydrochloric acid creatin is con- 

 verted into creatinin, and may be identified by its reactions. 



The preparation and detection of creatin is best performed by 

 the following method of NEUBAUER, which was first used in the 

 preparation of creatin from muscles. Finely-cut flesh is extracted 

 with an equal weight of water at -f- 55 to 60 C. for 10-15 minutes, 



Eressed and extracted again with water. The albumin is removed 

 rom the united extracts as far as possible by coagulation at boiling 

 heat, the filtrate precipitated by the careful addition of basic-lead 

 acetate, the lead removed from this filtrate by H 2 S and carefully 

 concentrated to a small volume. The creatin, which crystallizes in 



