4 22 Chemical Properties of Animal Fluids. [Dec. 



pitated in a state of chemical combination with the uric arid. It 

 is this compound which is gradually decomposed, and gives rise 

 to the crystallized superurate of ammonia. The deposit contains 

 none of the earthy phosphates. The muriatic acid digested with 

 the deposit, and then saturated with ammonia, precipitates 

 nothing. Subjected to fire, the deposit burns, and leaves at 

 length, and with some difficulty, a very small quantity of a fused 

 ash, which consists of carbonate of soda, proving that the deposit 

 often contains a small quantity of superurate of soda, that inso- 

 luble salt which, according to the experiments of Dr. Wollaston, 

 produces the gouty concretions of the joints. 



The secondary deposit of healthy urine, therefore, is not uric 

 acid, but a combination of this acid with an animal matter, 

 which appears to be a portion of the mucus of the bladder dis- 

 solved by the warm urine. The deposit contains still a trace of 

 superurate of soda, and by spontaneous decomposition there is 

 formed superurate of ammonia, which renders it crystalline. 



It is to be presumed that uric acid, which is deposited in the 

 bladder and forms calculi, contains this same animal matter, 

 which ought accordingly to be an essential constituent of all 

 calculi formed in the bladder. I have thus found it in two 

 different calculi which I examined with this view. The following 

 is the mode of separating the uric acid from the animal matter. 

 The calculus is dissolved in caustic alkali, and a precipitate 

 obtained by adding to the solution muriatic acid in excess. The 

 precipitate consists of uric acid; and a combination of the 

 animal matter with muriatic acid, which may be carried off by 

 washing the precipitate freely on the filter. The muriatic com- 

 pound is soluble in pure water, and is again precipitated by the 

 addition of muriatic acid, or by allowing it to drop into the acid 

 liquor which has passed through the filter. The uric acid re- 

 maining on the filter is in a state of purity greater than any that 

 has been hitherto the subject of examination. 



C. slnahjsis of Urine. 



I have - been at much pains to arrive at as accurate a know- 

 ledge as possible of the precise composition of urine, both as to 

 the quantity and condition of its constituents. The task has 

 been laborious, difficult, and often extremely complicated. It 

 would be trespassing on the patience of the Society, were I to 

 attempt at present to give an account of all the details, and such 

 is the nature of an exact analytical investigation that it admits 

 not of a brief recital. I shall therefore content myself .with 

 Communicating the general result, which is as follows : — 



1000 parts of urine are composed of 



