234 



On Siliceous Gravel. By Robert Venables, M. B., St. Mary 

 Hall, Oxford. 



Some foreign writers speak of urinary concretions consisting 

 of siliceous matter, in sufficient quantity to establish the cha- 

 racter of the species ; and Berzelius, in his treatise on the 

 blow-pipe, gives a formula for their discrimination*. He even 

 points out the characters distinguishing this class from those of 

 the phosphate of limef. From these circumstances, it might 

 probably be inferred, that siliceous deposits from the urine were 

 by no means of very rare occurrence. It does not, however, 

 appear that any of the British practitioners, who have been most 

 conversant with urinary disorders, have observed them either as 

 gravel, or as forming any sensible portion of urinary concretions. 

 Dr. Marcet has not mentioned its existence in any one of the 

 many calculi which he analyzed, and if it had existed it could 

 not have escaped so close and so accurate an observer. Dr. 

 Wollaston, I believe, has not met with it either ; and Mr. 

 Brande, in his Manual, does not speak of it as constituting 

 any portion of urinary calculi. Of 328 calculi — part of the 

 collection of the Norwich Hospital — analyzed by Dr. YellowleyJ, 

 there is not one stated to contain the smallest proportion of 

 siliceous matter. Hence then, it would appear, that in this 

 country, at least, urinary siliceous concretions are extremely 

 rare, and that, as yet, there has not been an instance recorded§. 



* " Alone," he says, " they leave an infusible scoriaceous ash, which 

 fuses with a small quantity of soda, slowly, and with effervescence, into a 

 more or less transparent glass globule." Berzelius on the Blow-pipe, 

 translated by Children, p. 332. 



f " A proof that these calculi (phosphate of lime) are not siliceous, 

 is, that they swell up with soda without vitrifying, and when dissolved 

 in boracic acid, and then fused with a little iron, they give a regulus of 

 phosphuret of iron." Ibid., pp. 330, 331. 



% Philosophical Transactions, 1829, part 1st. 



§ Of 600 calculi, analyzed with great care and exactness, by Fourcroy 

 and Vauquelin, only two were found to contain silica. Professor Wurzer 

 states, that he detected silica to the amount of one per cent, in a calculus 

 analyzed by him. Its composition he states to have been as follows : — 



Lithicacid . . . 75*34 



Phosphate of lime . . 17-33 



Animal matter . . 6*33 



Silica . . . .1-00 



100-00 



