240 Mr. Venables on Siliceous Gravel. 



acetic or muriatic acid the lime was dissolved, leaving the 

 lithic acid behind. On pouring off the acid, and adding 

 oxalate of ammonia, oxalate of lime precipitated, and was re- 

 cognised by its peculiar characters. The residual mass being 

 treated with potass, the lithic acid was dissolved and taken up. 

 Pouring off the solution, and supersaturating with vinegar, the 

 lithic acid was precipitated in the form of a whitish powder. 



The fact of these grains being covered with a coating of 

 known urinary origin, fully proves that they must have been 

 in contact with the urine sufficiently long to have had this coat- 

 ing deposited upon them. This could not have arisen from 

 their accidental contact with the urine in the cup, because the 

 urine was not acid, but neutral or rather alkalescent, as will 

 appear when we consider the properties of this fluid. But 

 further, they were not exposed to the action of the urine, after 

 being voided sufficiently long to have acquired Ahis coating. 

 Therefore, it must have been deposited or secreted upon them 

 in the kidney, or in some other part of the urinary organs. But 

 in order to place the question beyond dispute, I washed the 

 cup myself, and had the urine passed into it under circum- 

 stances which could not admit of deception, and I found the 

 same sand in the urine voided as above-stated. Hence, there 

 cannot be a doubt of their being passed with the urine from the 

 bladder. I have had several specimens brought to me, and 

 they all contain more or less of this siliceous matter. 



A detail of the treatment in these cases would be incon- 

 sistent with the object of the present communication, which is 

 the establishment of certain pathological facts, which have 

 been doubted, and upon which the authority hitherto has been 

 questionable. The morbid condition of the urine, however, is 

 a necessary preliminary to the future remarks, and, indeed, 

 essential to my purpose. I shall, therefore, proceed to this 

 detail in each case. 



In the first case, I received two specimens on the 27th of 

 May, 1828; — the one passed after dinner the preceding day, 

 was turbid from the mechanical suspension of a considerable 

 quantity of muco-purulent matter, mixed with the alkaline 

 lithates. On standing for a considerable time these subsided, 

 leaving a transparent amber-coloured urine floating above. 



