198 THE SECRETIONS: 



may be made in the following manner. Dilute hydrochloric 

 acid of known strength must be added guttatim to a weighed 

 quantity of gently warmed urine, till, from being alkaline, the 

 fluid becomes slightly acid. This point being attained, the 

 warmth is continued for some time in order to make sure that 

 the acid reaction is not due to the cavboaic acid that has been 

 liberated. The amount of carbonate of ammonia is then esti- 

 mated from the quantity of hydrochloric acid which has been used. 



10. Oxalate of lime. 



Oxalate of lime not unfrequently gives rise to urinary calculi. 

 A compound resisting a solvent power of the moderate acidity 

 of the urine cannot, of course, occur in it in a state of solution : 

 it has, however, been detected several times in urinary sediments, 

 for which reason I refer to it here. Prout and H. Brett 1 have 

 observed these sediments. The latter writer states that the 

 urine was very high-coloured, and that the sediment was of a 

 brownish tint. He ascertained its nature by its ready solubility 

 in dilute nitric acid without any indication being afforded of the 

 presence of uric acid, by its becoming white on incineration, by 

 the ash then dissolving in hydrochloric acid with considerable 

 effervescence, and by oxalate of ammonia producing an imme- 

 diate precipitate, while no marked effects followed the addition 

 of ammonia in excess : by these characters the oxalate of lime 

 was thoroughly and satisfactorily made out. I once found ox- 

 alate of lime in the urine of a man with induration of the 

 pancreas and suffering from great acidity of the stomach. The 

 urine was neutral, or all but alkaline, and contained the minute 

 prismatic crystals represented in fig. 36 d. They were insoluble 

 in acetic, but dissolved in hydrochloric acid ; and a further in- 

 vestigation left no doubt of their real nature. After some days 

 the urine became remarkably acid, and deposited a sediment 

 devoid of oxalate, but containing carbonate of lime. 



[I have already mentioned that oxalate of lime is a much 

 more common ingredient of urinary sediments than was formerly 

 supposed. (See Vol. I, p. 85.) In order to detect it, place 

 urine, passed a few hours after a full meal, in a large test- 



1 Urinary Diseases and their Treatment. By Robert Willis, M.D. p. 118. 



