502 URINE. [CHAP, xxxiv. 



Creatine (C 8 H 9 N 3 4 ) occurs in very small quantity in the urine. It is a 

 colourless crystalline body, with a strong pungent taste, soluble in cold and 

 very soluble in boiling water ; it is almost insoluble in alcohol. Boiled with 

 baryta water, it becomes changed into urea and sarcosine ; and it is probable 

 that a somewhat similar decomposition ensues within the organism, and that 

 of the quantity of creatine formed in the muscular fibre, a large portion is 

 eliminated from the system in the form of urea, and partly, perhaps, as car- 

 bonic acid and ammonia. 



Creatine was obtained in the beautiful investigation of Liebig from the 

 flesh of various animals ; but the proportion in which it exists is so small, 

 that it can only be extracted with great care, and by operating upon large 

 quantities. It occurs most abundantly in the flesh of fowls, and in the heart 

 of the ox. 



Creatinine (C 8 H 7 N 3 2 ) is also met with in the urine, and its presence in 

 this fluid was discovered by Liebig, to whom we are indebted for all that is 

 known in reference to this body. Creatinine crystallises in colourless crystals. 

 It possesses a hot burning taste, compared to caustic ammonia. It is soluble 

 in water, and, unlike creatine, is freely dissolved by spirit. It is found with 

 the last-mentioned body in the juice of muscular fibre. Creatinine may be 

 formed by the action of hydrochloric acid upon creatine, a change which 

 renders it probable that it is also formed from the last-named body in the 

 organism. In urine, creatinine exists in larger quantity than creatine ; while 

 in muscular fibre the latter is found to exceed the former in amount. 



Extractive Matters. Under this very unsatisfactory term are included cer- 

 tain substances met with in the urine, blood, and other animal fluids, which 

 are not easily isolated, whose properties are with great difficulty determined, 

 which do not crystallize, are not volatile without decomposition, and cannot 

 be obtained in a pure form. Of late years, however, several substances have 

 been separated from the extractive matters, which were formerly included 

 under that term. Of these, albuminate of soda, creatine, and creatinine may 

 be referred to as examples. These extractive matters no doubt play a most 

 important part in vital chemistry, and probably represent a stage intermediate 

 between the nutritive pabulum and the tissues formed from it, or between 

 the latter in process of disintegration and the compounds we have been con- 

 sidering, such as urea, lithic acid, etc., but in the present state of cur know- 

 ledge, little beyond mere speculation can be advanced. 



Our friend, Dr. G. O. Rees, found that, in cases of albuminuria connected 

 with kidney disease, large quantities of the extractive matters of the blood 

 passed off in the urine as well as albumen. The test which Dr. Rees employed 

 for detecting the presence of the blood-extraction was the tincture of galls.* 



Ammoniacal Salts. Ammonia exists in very small quantity, if indeed it 

 be present in healthy urine, but in disease a considerable proportion may 

 occur It has been found as hydrochlorate, lactate, biphosphate, ammonio- 

 magnesian or triple phosphate, and in the form of phosphate of ammonia and 

 soda. Its presence usually depends upon the decomposition of some of the 

 nitrogenous constituents of the urine, as previously indicated. 



Fixed Salts. By the careful incineration of urine we obtain the fixed salts, 

 and we find that, of the saline residue, part is soluble and part insoluble in 



Lettsomian Lectures. London Medical Gazette, vol. xlviii. 1851. 



