207 



the occurrence of silica in calculi in determinate amount. Those in 

 which the largest proportions were found are placed first. A fuller 

 account than can be given here, will be found in a paper in the 

 Boston Medical and Sm-gical Journal of June 20, and another 

 which will appear in the same Journal of September 19. 



I. A calculus from the urethra of a lamb. Analyzed by Lassaigne 

 in 1830. Proportion of silica about -^-q-. Remainder, animal matter, 

 and a trace of oxide of iron. This calculus is usually reported as 

 wholly composed of silica. 



n. A calculus from the urethra of an ox, killed on account of re- 

 tention of urine caused by it. Analyzed by myself. Contains 80 

 per cent, of silica, with a little carbonate and phosphate of lime, and 

 animal matter. In this, and in other siliceous calculi, analyzed by 

 me, the siKca occurs, partly at least, as a hydrate. 



III. A collection of over six hundred little spherical calculi from 

 an ox-bladder. Analyzed by myself. Silica forms 78 per cent. ; 

 with water, and a little chloride of potassium, and other potash and 

 soda salts. It is not uncommon to find calculi in ox-bladders, resem- 

 bling these in appearance, but composed of carbonate of lime. 



IV. A calculus, analyzed by Fourcroy and Vauquehn, about 1798, 

 and stated to be from the human bladder. Silica formed about | of 

 the nucleus and two inner layers, and was not present in the three 

 outer layers. 



V. A calculus from the kidney of a sheep, analyzed by myself. 

 It contains about 50 per cent, of silica ; with carbonate of lime, car- 

 bonate of magnesia, and organic matter, 



VI. A calculus from the urethra of an ox, analyzed by myself. 

 The animal died from rupture of the bladder, caused by the impacted 

 calculus. Silica forms about 43 per cent. The other constituents 

 are 29 per cent, of carbonate of lime ; 5 per cent, of carbonate of 

 magnesia ; some animal matter ; with water, and traces of phosphate 

 of lime and oxide of iron. 



VII. A calculus from the urethra of a bull, analyzed by Wurzer 

 in 1833. It had the size and form of a small bean, and contained 

 38.5 per cent, of silica, and 36.3 per cent, of carbonate of lime. 



Vni. A calculus from the urethra of an ox, whose death was 

 caused by it. Analyzed by Wurzer in 1822. In size and shape, it 

 resembled a small bird's egg. SiHca formed 38.2 per cent, and car- 

 bonate of lime 36.8 per cent. 



IX. A collection of four little calculi from the kidney of an ox. 

 One, analyzed by Mr. R. Crossley, several years since, consisted 

 mostly of carbonate of lime, with a trace of phosphate of lime and 

 peroxide of iron, some animal matter, and also silica. The propor- 



