382 THE URINE. 



eliminated 1807.60 grains of nitrogen, in the urine and feces. This 

 leaves 633.80 grains of nitrogen, over and above the nitrogen of the food, 

 which must be attributed to the waste of his tissues, and probably 

 almost exclusively to the waste of his muscular tissue. According to 

 the best authorities, lean meat uncooked, or muscular tissue, contains 3 

 per cent, of nitrogen. The loss of 633.80 grains of nitrogen would then 

 represent a loss of 21,121.00 grains, or 3.018 Ibs. of muscular tissue. 

 The actual loss of weight was 3.450 Ibs. This allows about 0.43 Ib. of 

 loss unaccounted for, which might be fat or water." 



Creatinine. This substance is perhaps next in physiological import- 

 ance to the urea, considering its analogy in chemical composition, but 

 is produced in much smaller quantity ; its total amount usually not ex- 

 ceeding 1 gramme per day. It has not been found in any of the solid 

 tissues ; but it is probably derived by transformation of the creatine of 

 the muscles, since it may be artificially produced from the latter by the 

 action of heat and dilute sulphuric acid. It is undoubtedly, like urea, 

 a product of the metamorphosis of the albuminous ingredients of the 

 body, from which it derives its nitrogenous element. But little is known 

 with regard to the conditions which increase or dimmish its production. 



Sodium and Potassium Urates. The urates are due to a combination 

 of the alkaline base with a nitrogenous mineral acid, belonging to the 

 same physiological class of excrernentitious matters as urea and creati- 

 nine. This substance is known to be, like urea, increased in quantity 

 by a nitrogenous, and decreased by a non-nitrogenous diet ; but its rela- 

 tions to muscular exercise and other temporary conditions are not fully 

 known. The urates are readily soluble in water, and are usually excreted 

 to the amount of about 1.75 gramme per day. The hippurates have, in 

 general, similar chemical and physiological relations to those of the 

 urates, excepting that they are more abundant under the use of a vege- 

 table diet, and disappear altogether when the food is exclusively of an 

 animal nature. In the human subject under an ordinary mixed diet, 

 they amount to about one-half the quantity of the urates. 



The preceding ingredients of the urine are all associated in a single 

 physiological group, forming its nitrogenous excrementitious substances. 

 Beside them, it also contains a variety of inorganic or mineral constitu- 

 ents, derived from the waste of the animal tissues and fluids. 



Acid Sodium Phosphate, or sodium biphosphate. This is the ingre- 

 dient which gives to the urine its acid reaction to test-paper. It is 

 regarded as derived from the ordinary sodium phosphate of the blood 

 (Xa. 2 H P0 4 ) by the action of the uric acid produced in the system, which 

 unites with a part of its sodium, forming sodium urate, and leaving an 

 acid sodium phosphate (NaH Q POJ. The uric acid produced from the 

 decomposition of animal substances, although it does not itself appear 

 in a free form, is, therefore, indirectly the cause of the acid reaction of 

 the urine ; and this reaction will vary in intensity with the amount of 

 uric acid discharged. 



