206 EXCRETION. 



cosine ; but the recent researches of Yoit have pretty con- 

 clusively shown that this change does not take place in the 

 living organism, and that probably none of the urea of the 

 urine is produced in this way. 1 "When boiled with the strong 

 acids, creatine(C 8 H 9 O 4 N 3 + 2HO) loses four atoms of water, 

 and is changed into creatinine (C 8 H 7 O 2 N 3 ). This change 

 takes place very readily in decomposing urine ; which con- 

 tains neither urea nor creatine, but a large quantity of crea- 

 tinine, when far advanced in putrefaction. 



Creatinine is more soluble than creatine, and its watery 

 solution has a strong alkaline reaction. It is dissolved by 

 eleven parts of cold water, and is even more soluble in 

 boiling water. It is slightly soluble in ether, and is dis- 

 solved by one hundred parts of alcohol. This substance is 

 regarded as one of the most powerful of the organic bases, 

 readily forming crystalline combinations with a number of 

 acids. According to Thudichum, who has very closely stud- 

 ied the physiological relations of these substances, creatine 

 is the original excrement itious principle produced in the 

 muscular substance, and creatinine is formed in the blood 

 by a transformation of a portion of the creatine, somewhere 

 between the muscles and the kidneys ; " for, in the muscle, 

 creatine has by far the preponderance over creatinine ; in 

 the urine, creatinine over creatine." ' 



In the present state of our knowledge, there is very little 

 to be said with regard to the physiological relations of crea- 

 tine and creatinine, except that they are probably to be 

 classed among the excrementitious principles resulting from 

 the disassimilation of the muscular tissue. As they exist 

 in considerable quantity in the muscular substance, it be- 

 comes a question whether, in the urine of carnivorous ani- 

 mals, they are not derived from the food ; but they could 

 have no such origin in the herbivora, nor in the urine of 



1 VOIT, Ueber das Verlialten des Kreatins, Kreatinins und Harnstoffs im Thier- 

 korper. Loc. cit., p. 116. 



2 THUDICHUM, Pathology of the Urine, London, 1858, p. 120. 



