298 On Gravelhj and Calculous Co7icretion3, 



The constant opportunity I liave of attending to tho5e 

 eubjects, enables me to say, that the urine of gravelly pa- 

 tient^, \\ hen fresh rendered, nay, after standing many hours, 

 in a temperature of sixty degrees, is relatively more acid 

 than the healthy, sometimes as much so as the gouty ; and 

 frequently continues so, even after depositing its gravelly 

 matter. An exception to this, however, sometimes occurs 

 in gouty habits ; their urine depositing copiously this acid 

 substance, and yet manifesting no increased, but sometimes 

 rather decreased, acescency ; for with them a considerable 

 diminvition of the quantity of the usually excreted super- 

 acidulated phosphoric salt often takes place, as shall be 

 fully explained upon another occasion. 



Having premised these observations, it is now time to 

 consider what effects acid substances are productive of, 

 when mixed, oiU of the body, with this very complicated 

 liquor. And here, to prevent repetition, I wil! observe, 

 that that generallv used was rendered fresh in the morning, 

 in the quantity of from three to four ounces, (unless other- 

 wise specified,) being that mos-t easily retained at orve time 

 in the bladder. The quantity of acid extremely small, for 

 obvious reasons, and seldom increasing its acescent prO' 

 perties (as ascertained by the usual tests) beyond wdiat fre- 

 quently occurs in the urine of those who use acescent drinks, 

 or are afflicted with gout or gravel. A standard quantity 

 was always laid by for comparison ; and the temperature 

 from sixty to seventy-five degrees, being in autumn 1799' 

 And to begin with the vegetable acids :-^ 



Experiment I. 



To four ounces of the urine of an adult was added one 

 drachm of common acetous acid, which, like every other 

 acid, caused no immeuiate change in it; but in a very short 

 time, and before it cooled down to the temperature of the 

 atmosphere, some extremely minute shining spiculae, ob- 

 servable only by a lens, were seen floating in it : these gra- 

 dually increased in number and size, began to reflect the 

 light, and, from being perfectly transparent, soon became 

 coloured, to settle upon the usual cloud, or nubecula, 

 which now began to form, adhere to the sides of the glass, 

 and partly fall to the bottom in the shape of small bright 

 red crvstals. In ihe standaj-d, after twelve hours, nothing 

 more observable than the usual mihecula ; nor was there any 

 eign of crystallization, or separation of uric acid, even aher 

 twenty-lour. 



Lxperhnent 



