vii KATABOLIC CONSTITUENTS OF URINE 409 



in Cetti's 10 days' fast, and explained it logically on the assumption 

 that during inanition the bone tissues, which are rich in phosphates 

 and poor in nitrogenous substances, are used up. Evidence in 

 favour of this assumption is afforded by the fact that in fasting 

 the amount of calcium and magnesium, which are the bases of the 

 bone phosphates, also increase in the urine. The excretion of 

 phosphates in fever, which is almost always accompanied by more 

 or less accentuated phenomena of inanition, should be further 

 investigated, in view of this important fact observed during 

 complete abstinence. 



According to Ott's researches the influence of diet appears 

 plainly in the daily curve of the total elimination of phosphates, 

 which rises and reaches its maximum in the hours that succeed 

 the principal meal, and falls again in the night hours, reaching its 

 minimum in the hours that precede a meal. 



The carbonic acid of the urine occurs partly in a free state, 

 partly combined as carbonates, and bicarbonates with soda, lime, 

 magnesia, and ammonia, which are specially abundant in the 

 fresh, alkaline urine of herbivora. 



Free carbonic acid, according to Planer, is present in human 

 urine to an amount of 4-9 vols. per cent according to Pfliiger of 

 13-14 vols. per cent. The partial pressure of the CO 2 in the 

 urine is somewhat higher than in the blood (according to 

 Strassburger it is equal to -^ of an atmosphere), and rises some- 

 what in fever (Ewald). 



The amount of combined carbonic acid in human urine is 

 usually less than that present in the free state (2'5 vols. per cent 

 according to Planer, 0'1-0'7 vols. per cent, according to Pfliiger), 

 and does not increase in fever (Ewald). The carbonates and 

 bicarbonates are alimentary, or come from the lactic, malic, 

 tartaric, succinic, and other vegetable acids introduced with the 

 foods, which are readily oxidised by conversion into carbonates. 

 This is the reason why the urine of herbivora and vegetarians is so 

 rich in carbonates, which give it an alkaline reaction, and cause it 

 to become turbid shortly after emission. On filtering off the 

 deposit, it is found to consist of calcium carbonate and phosphates. 



Among the inorganic bases contained in urine, special mention 

 must be made of ammonia. Only a trace can be detected in the 

 free state previous to the commencement of alkaline fermentation, 

 in which the urea is converted into ammonium carbonate. The 

 chief part of the ammonia is found in the form of ammonium 

 salts (phosphates, carbonates, etc.) to an average daily amount of 

 0'7 grm. (Neubauer). For the same person, Coranda found 0'64 

 grm. after an ordinary mixed diet, 0'S7 grm. after a flesh diet, 

 0'64 grm. with a vegetable diet. The influence of alimentation 

 on the ammonia content of the urine is therefore striking. 



Injection of ammonium salts increases the amount present in 



