CREATIN AND CREATININ 345 



Hippuric acid itself, unlike uric acid, is soluble in water and in a 

 mixture of hydrochloric acid. It requires six hundred parts of cold 

 water for its solution, but a much smaller proportion of warm water. 

 Under pathological conditions it is sometimes found free in solution in 

 the urine. 



Sodium, potassium and calcium lactates exist in considerable quan- 

 tity in normal urine. They are derived immediately from the blood, 

 passing ready-formed into the urine, where they exist in simple watery 

 solution. The lactates are formed in the muscles, in the substance of 

 which they can readily be detected. Physiologists have little positive 

 information in regard to the precise mode of formation of these salts. 

 It is probable, however, that the lactic acid is the result of transforma- 

 tion of glucose. The lactic acid contained in the lactates extracted from 

 the muscular substance is not identical with the acid resulting from the 

 transformation of the sugars. The former have been called sarcolactates, 

 and they contain one molecule of water less than the ordinary lactates. 

 The compounds of lactic acid in the urine are in the form of sarcolac- 

 tates. 



Creatin and Creatinin. Creatin(C 4 H 9 N 3 O 2 ) and creatinin (C 4 H 7 N 3 O) 

 probably are identical in their relations to the general process of ka- 

 tabolism, for one is easily converted into the other, out of the body-, by 

 very simple chemical means ; and there is every reason to suppose that 

 in the organism they are the products of physiological wear of the same 

 tissue or tissues. These substances have been found in the urine, blood, 

 muscular tissue and brain. By certain chemical manipulations, both 

 creatin and creatinin may be converted into urea. These substances 

 are now regarded as excrementitious matters, taken from the tissues by 

 the blood, to be eliminated by the kidneys. 



Creatin has a bitter taste, is quite soluble in cold water (one part 

 in seventy-five), and is much more soluble in hot water, from which it 

 separates in a crystalline form on cooling. It is slightly soluble in alco- 

 hol and is insoluble in ether. A watery solution of creatin is neutral. 

 It does not readily form combinations as a base ; but it has lately been 

 made to form crystalline compounds with some of the strong mineral 

 acids nitric, hydrochloric or sulphuric. When boiled for a long time 

 with barium hydrate, it is changed into urea and sarcosin. When boiled 

 with the strong acids, creatin loses a molecule of water and is converted 

 into creatinin. This change takes place readily in decomposing urine, 

 which contains neither urea nor creatin but a large quantity of creatinin, 

 when far advanced in putrefaction. 



Creatinin is more soluble than creatin, and its watery solution has 

 a strongly alkaline reaction. It is dissolved by eleven parts of cold 



