302 On Gravelly and Calculous Concretions. 



acid. Tn less thati an hour the former deposited a dlstincf 

 quantity of gravelly matter in considerable proportion. This, 

 perhaps, we should not be surprised at, when \vc consider 

 how the action of this acid in that fluid may be determined 

 by superior affinity. In the latter the separation did not 

 tfake place for a considerable time after. We see, then, that 

 the nitrous acid speedily and powerfully precipitates this 

 acid substance. 



Experanenl XIII. 



To six ounces of urine, showing a strong acescent qua- 

 lity, were added only three drops of strong marine acid. 

 A cloudiness and transparent granular precipitation took 

 place, followed by the formation of extremely minute gra- 

 velly concretions, which, even after two days standing, did 

 tiot'assumc so red a tinge as that with vegetable acids. This 

 mav probably depend upon .some action of this acid upon 

 the'urce, or' colouring matter; but as to the smallness of 

 the crystals, that cvidenilv depends upon the more speedy 

 precipitation, throwing them down before they can assume 

 their natural size, and"leaving but a shade of diflerence be- 

 tween the crystalline and pulverulent deposits. 



Jlrcperiment XIV, 



Froiii the above, then, we are satisfied that the vegetable 

 and mineral acids cause a premature separation and crystal- 

 lization of the lithic contents of recent healthy urine ; but 

 it nuiv be observed that this or.ly takes place under circum- 

 stances not at all applicable to the living system, viz. a 

 much inferior temperature, and, in some iit-stances, a con- 

 tact with the otnlospheric air; two powerful promoting 

 causes of crystallization in general, but more especially of 

 the less soluble salts. To determine, therefore, this most 

 essential point : 



To six ounces of cold but recent urine (in a well closed 

 Tjhial) were added five drops of very dilute nitrous acid, 

 which were placed on a sand bath : temperature varying 

 from 80 to ai)out 100 degrees at most. The same quantity, 

 with similar precautions, but without addition, was laid 

 aside in the laboratory as a standard: temperature 56 de- 

 crees. After a very short interval indeed, and almost aa 

 soon as the urine acquired the temperature of between 80 

 and 90 degrees, small shining graiudar pai tides were ob- 

 servable with a magnifier, began gradually to settle upon a 

 broken kind of nubecula or rather nubeculre, and to acquire 

 colour and sIjjc, tliovigh carried up and down the liquor, 

 which was in constant agitation. This experiment again 



twice 



