ACIDS OF THE URINE. 781 



base, having a strong alkaline reaction, and forming crystallizable 

 salts with acids. Creatin exists in large quantities in the juice of 

 muscle, from which it was first prepared by Liebig. Creatinin is 

 present only in small quantity in the juice of flesh, but is readily 

 formed by the action of strong acids upon creatin. Creatin appears 

 to be, with succinic acid, a product of the decomposition of syntonin, 

 whilst creatinin results from still further decomposition ; from its basic 

 nature, it approaches in character to urea, into which substance, and 

 sarcosin, it is decomposed by the action of baryta at the boiling-point. 

 Albumen may be broken up artificially, by the action of powerful acids 

 or alkalies, into glycocoll, tyrosin, and leucin, nitrogenous bodies inter- 

 mediate between it and urea. By the action of caustic alkalies on 

 creatin, urea is formed, whether through the previous formation of 

 creatinin is not certain. Albumen, creatin, creatinin. and urea, form, 

 therefore, a descending series of nitrogenous bodies. Both creatin and 

 creatinin are more abundant in exercised muscles, and, therefore, 

 would seem to be products of muscular action; both substances are 

 present, in small proportions, in healthy blood, from which they are 

 excreted, also in small quantity, by the kidneys. They are supposed 

 to be transformed chiefly into urea, probably through the agency of 

 the epithelial cells of the uriniferous tubes, and, thus changed, finally 

 enter the urine. Creatin and creatinin, therefore, are compounds 

 probably preformed in the body, i. e., in the muscles, thence entering 

 the blood by venous absorption ; they are excreted from it, in minute 

 quantity, in their proper form, but chiefly after conversion into urea. 

 They are the principal immediate source of the last-named substance, 

 which is even associated with them in the juice of the flesh of certain 

 Cartilaginous Fishes. (Frerichs and Stadeler.) 



The coloring substance of the urine, urinary pigment or uro-haema- 

 tin, contains iron, and is separable into red, blue, and yellow coloring 

 matters, named uro-rhodin, uro-glaucin. and uro-xanthin. Their nature 

 is not well understood ; they exist but in small quantity, and are very 

 prone to decomposition. According to some, these pigments are allied 

 to indigo, and its derivatives, indigo-red, indigo-blue, and indican. 

 The blue pigment, or uro-cyanide, is named the indigo of urine. 



The non-crystallizable extractive matters of the urine exist in large 

 quantities, and require further investigation ; they are nitrogenous 

 bodies, some even containing sulphur and phosphorus, probably derived 

 from the albuminoid tissues ; they are liable to decompose, and are 

 abundant in certain diseased conditions. 



Traces of mucus and epithelium, either of the spheroidal glandular 

 kind from the tubuli, or of the squamous kind from the interior of the 

 bladder, also occur, as cloudy deposits, in this excretion. 



There are also several non-nitrogenous, hydro-carbonaceous, or car- 

 bonaceous substances in urine. Thus, lactic acid, C 3 H 6 3 , occurs occa- 

 sionally, as, e. g., when that acid, or some of its salts, are present in 

 large quantity in the blood, owing to feeble conditions of .the respira- 

 tory process, or to defective oxidating processes in the blood. By 

 Lehmann, lactic acid is said to be constantly present, and to be the 

 cause of the acidity of the urine ; but, by others, this is supposed to 



