418 



EXCRETION. 



hydrochloric acid. It requires six hundred parts of cold water for its solution, and a 

 much smaller proportion of warm water. Under pathological conditions, it is sometimes 

 found free in solution in the urine. 



The lactates of soda, potassa, and lime, exist in very considerable proportion in the 

 normal urine. They are undoubtedly derived immediately from the blood, passing 

 ready-formed into the urine, where they exist in simple watery solution. According to 

 Robin, the lactates are formed in the muscles, in the substance of which they can be 

 readily detected. We have no positive information with regard to the precise mode of 

 formation of these salts. It is probable, however, that the lactic acid is the result of 



FIG. 120. Crystals ofhippuric acid. (Funke.) 



FIG. 121. Lactate of lime, from chemically pure 

 lactic acid and carbonate of lime, crystal- 

 lised from a hot, watery solution. (Funke.) 



transformation of glucose. As a curious chemical fact, it is interesting to note that the 

 lactic acid contained in the lactates extracted from the muscular substance is not abso- 

 lutely identical with the acid resulting from the transformation of the sugars. The for- 

 mer have been called sarcolactates, and they contain one equivalent of water less than 

 the ordinary lactates. According to Robin, the compounds of lactic acid in the urine are 

 in the form of sarcolactates. 



Although the inosates have never been detected in the urine, Robin is of the opinion 

 that traces of these salts are separated from the blood by the kidneys, from the fact that 

 they exist normally in the blood and in the muscular tissue. 



We have little or no information with regard to the relations of the inosates to ex- 

 cretion. 



Creatine and Creatinine. Creatine and creatinine are undoubtedly 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 reason to 

 suppose that, in the organism, they are the products of physiological waste of the same 

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

 and brain. Scherer has demonstrated the presence of creatine in the amniotic fluid. By 

 certain chemical manipulations, both creatine and creatinine may be converted into urea ; 

 and the fact that these substances are now known to be constant constituents of the 

 urine leaves no doubt that they are to be classed among the excrementitious principles. 

 Chevreul, who first discovered creatine in the extract of muscular tissue, regarded it as 

 one of the nutritive principles of meat ; but the subsequent researches of Heintz, Liebig, 

 and others, who found it in the urine, revealed its true character. Verdeil and Marcet 

 have since found both creatine and creatinine in the blood ; and these principles are now 



