EXCRETION BY THE SKIN AND KIDNEYS. 



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

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

 formation of the sugars. The former 

 have been called sarcolactates, and they 

 contain one equivalent of water less 

 than the ordinary lactates. The com- 

 pounds of lactic acid in the urine are in 

 the form of sarcolactates (Robin). 



Creatine and Creatinine. Creatine 

 (C 4 H 9 N 3 2 ) and creatinine (C 4 H 7 N 3 0) 

 are probably identical in their relations 

 to the general process of disassimilation, 

 for one is easily converted into the 

 other, out of the body, by very simple 

 chemical means ; and there is every rea- 

 son to suppose that in the organism, 

 they are the products of physiological 

 These substances have been found in the 

 urine, blood, muscular tissue and brain. Scherer has demonstrated the pres- 

 ence of creatine in the amniotic fluid. By certain chemical manipulations, 

 both creatine and creatinine may be converted into urea. Verdeil and Mar- 

 cet have found both creatine and creatinine in the blood ; and these sub- 

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

 by the blood, to be eliminated by the kidneys. 



Creatine has a bitter taste, is quite soluble in cold water (one part in sev- 

 enty-five), and is much more soluble in hot water, >from which it separates in 



FIG. 122. Crystals of hippuric acid (Funke). 



wear of the same tissue or tissues. 



FIG. 123. Creatine, extracted from the muscu- 

 lar tissue, and crystallized from a hot, wa- 

 tery solution (Funke). 



FIG. 124. Creatinine, formed from creatine by 

 digestion with hydrochloric acid, and crys- 

 tallized from a hot, watery solution (Funke). 



a crystalline form on cooling. It is slightly soluble in alcohol and is insolu- 

 ble in ether. A watery solution of creatine 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 and 



