237 



Chimiques, and the Memoires of the National Institute; 

 not proposing to go into their chemical properties, farther 

 than may be necessary to my present inquiry; namely, of 

 how far acids may be conducive to the formation, or al- 

 kalescent substances to the prevention, or even solution, 

 of a large proportion of gravelly and calculus concretions. 

 We have already remarked, that, to the sagacity of Boer- 

 haave, we are indebted, for the knowledge of gravelly mat- 

 ter being a constituent part of urine, kept in chemical 

 solution in it; and, happily for mankind, only separable 

 from it, after being some considerable time out of the 

 body. After minutely detailing the ingenious means made 

 use of by Boerhaave, to ascertain this important point, to 

 which I beg leave to refer, his commentator. Van Swie- 

 ten, goes on to observe. 



" Hoc calculi rudimenta adsunt etiam in urina homi- 

 " num sanissimorum ; quae, si luia cum urina secemuntur, 

 " antequam ab urina secesserint, et concrescere inceperint, 

 " nullo modo sanitatem Isedent. Cum autem observatum 

 " fuevit, illam separationem rudimentorum calculi citius 

 " fieri in quibusdam hominibus, tardius in aliis, patet, 

 " illos magis calculo obnoxios vivere, in quibus citius haec 

 " scparatio arenularum obtinet. An quandoque ilia sepa- 

 " ratio contingit jam in renibus, et in vesica, antequam 

 " urina expellatur de corpore? Certe videtur. Vidi saepius, 

 " una cum urina excretum sabulum nephriticum expulsum 

 " fuisse, statimque, calente adhuc et fumante urina, in 

 ^■fundo matulae subsedisse. Contigit aliquoties, inventam 



VOL. X. u h " fuisse 



