414? Mr. T. Taylor's Observations on Urinary Calculi 



Uric acid; Urate of ammonia : Phosphates ... 3. 



Ditto Oxalate of lime : Ditto l. 



Urate of ammonia : Uric acid: Phosphates ... l. 



— Oxalate of lime: Ditto ... 13. 



Ditto Uric acid ... 1. 



' Urate of ammonia 1. 



Oxalate of lime : Uric acid: Ditto l. 



■ Oxalate of lime 1. 



Calculi consisting of several layers 8. 



Uric Acid. — Of these calculi, the greater number has been 

 taken from adults; the finest specimen, which is remarkably 

 compact and crystalline, was extracted by Mr. Lawrence from 

 the bladder of a man aged 72: some few contain a little urate 

 of ammonia, and in these a minute quantity of oxalate and 

 phosphate of lime may be detected. 



Urate of Ammonia. — In no table that has been given by 

 writers on this subject has urate of ammonia been regarded 

 as forming an independent concretion, and its existence as 

 such has been much disputed. This difference in opinion has 

 arisen from the difficulty of separating this salt, in an unex- 

 ceptionable manner, from the triple phosphate with which it 

 is frequently mixed. 



The chief chemical evidence adduced in favour of its pre- 

 sence, is the evolution of ammonia when these calculi are 

 treated with a solution of caustic potash. It has been con- 

 tended, on the other hand, that the ammonia is derived from 

 the decomposition of the phosphate of ammonia and magnesia, 

 or of urea accidentally present. When the former is the case I 

 am not aware of any method by which this objection can be set 

 aside, for every plan which I have hitherto tried of separating 

 these salts so as to avoid their reaction on each other has failed. 

 There are, however, many calculi in which the presence of 

 urate of ammonia can be satisfactorily shown, and which con- 

 tain none of the triple phosphate, or which contain it in so 

 small a quantity as to be inadequate to account for the quantity 

 of ammonia combined with the uric acid; and as these calculi 

 possess the same external appearances, and in their general 

 chemical characters correspond exactly with those containing 

 the phosphate of ammonia and magnesia, I think it fair to 

 infer that their composition is similar. Notwithstanding there- 

 fore the deservedly high authorities by which the contrary 

 opinion has been maintained, I must fully concur in the ob- 

 servation of Dr. Prout, that all those calculi which present 

 when broken an amorphous and earthy-looking fracture, con- 



