On Gravilhj and Calculous Coiicretions. 205 



clto in urlna concrescat. Felices llli, in quibus tardissime hoc 

 fit. Propriam saepius examinavi uriuani, laetusque vidi, ru- 

 dimenta ilia prima calculi separari quam tardissime, rcqiiiri 

 quandoque horas viginti quatuor et ultra, antequam in sa- 

 bulum majoris molis concrcsccre potucrint. Sed ct, licet 

 decinium tertium aetatis lustrum cmeusus jam fuerim, ab 

 omni lithiasi immunis vixi." 



The nVode and appearances attending the separation and 

 crystallization oF this substance from healthy urine, is one 

 of" the most beautiful that, probably, chemisiry affords. 

 But, as the circumstances arc so minutely and correctly 

 detailed bv Boerhaave, and his commentator, Van Svvieten, 

 in his treatise De Culcido, vol. v. p. 201 and 202, and cor- 

 respond so much with my own experiments, so often re- 

 peated, I must refer to him. On this passage, however, I 

 must observe, thr.t the space of twenty-four hours, men- 

 tioned by him as the period of spontaneous separation, is 

 by far, in the healthy state, too short, and that it extends 

 to two, three, and sometimes more davs, according to tlie 

 existing temperature and other circumstances. Nothing, 

 therefore, I will presume to say, is more erroneous than 

 the assertion, repeated in almost every chemical book, that 

 the uric acid separates from urine upon cooliiig. When 

 this occurs, which frequently happens, particularly with 

 children, the urine is certainly surcharged with this very 

 insoluble substance. 



An increased temperature hastens the incipient decom- 

 position of urine, and its first am moniacal degeneration is- 

 always attended by the deposition of its uric acid in its crys- 

 talline form. 



This did not escape the observation of Jlales, who tellfi 

 us, that urine, tending to putrefaction, affords most of this 

 acid substance ; and, indeed, were it to be deposited upon 

 cooling, or within the space of twenty-four hours, or eveiv 

 more, as is so generally asserted, it should every day pre- 

 sent itself to physicians, who so constantly attend to the 

 state of urine in glasses ; but this is by no means the case: 

 and we find Fourcroy, in his last publication, mentioning 

 from twenty-four to forty-eight hours, which certainly only 

 applies fo sunnner heat, or the circumstance already men- 

 tioned. 1 



Our next great obligation is, undoubtedly, to Schecle, 

 who has made us acquainted with its nature, and the very 

 distinct chemical projierties already enumerated. 



While in the slate of gravel it is ever the same, whether 



passed 

 .3 



