231 



which may probably prove interesting, in a practical point 

 of view. 



These, with some observations, and deductions fi'om 

 them, I now, with diffidence, offer to the candor and con- 

 sideration of the Academy. 



I must here premise, that the limits of an academic 

 dissertation necessarily confine me, chiefly, to the consi- 

 deration of gravelly matter itself, and that species of cal- 

 culus, which most generally results from its aggregation. 



Though determined to intrude as little as possible on 

 their time, by an useless quotation from ancient authors, 

 who could have no clear ideas of the subject: yet the 

 better illustration of my object, as well as a sense of jus- 

 tice, oblige me to go as far back as Van Helmont, whose 

 great, though eccentric genius first observed, that the sub- 

 ject matter of calculus existed in the urine itself. But 

 the flighty extravagance of his ideas, of which he has 

 given us a specimen on this subject, in his Treatise de 

 Lithiasi, (a wonderful production for the time,) caused lit- 

 tle attention to be paid to his opinion; and it was reserv- 

 ed for the capacious and learned genius of Boerhaave, first 

 to ascertain, beyond future doubt, the presence of gravel- 

 ly matter, as a natural constituent part of urine, kept in 

 chemical solution in it, and eliminated by it, out of the 

 system. Of this important fact, no material use was made, 

 until the all-prying genius of the immortal Linnaeus in- 

 duced him to request his friend Scheele, to turn, for a 

 moment, his great chemical abilities, to the investigation 



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