Of these 311, in 97 much free acid was passing from the system, as so often layers of

uric acid occur.

38 but little free acid was thrown

out, as so often mixed layers of urate of ammonia and uric acid appear in the Table.

117 no free acid passed, although litmus was reddened.

59 the state of the secretion is un

known, the oxalate of lime not

offering any indication of it.

Omitting these 59 oxalate of lime, there are then 117 states in which no free acid is passing from the system, and 135 in which little or much free acid was thrown out. From this it appears that in 252 cases of the uric acid diathesis, there were 187 in which no free acid was passing, and in these, alkalies would be of no benefit, so far as neutralising free acid in the urine is concerned: that is, in nearly every second case of the uric diathesis, there was but little any free acid in the urine to be neutralised.

if

In only 97 cases out of 252 was there much free acid secreted, or only twice in five cases were alkalies very necessary to remove the acidity of the urine; though in other cases these medicines might have been beneficial in some other respect.

There are two points in my analysis which I have found difficult of determination, when only a small quantity of the calculus or layer could be spared.

The first, which is rare, is, to distinguish between

a mixture of urate of ammonia with oxalate of lime, and urate of ammonia with urate of lime. The other is to recognise a mixture of uric acid with urate of ammonia. There is no difficulty in either case when a sufficient quantity of the calculus can be spared. The microscope, which in fresh sediments on the last question is most satisfactory, with the powder of calculi has afforded me no assistance.

In 40 cases the phosphates or the phosphates and carbonates form the last layer.

In 7 cases the whole calculus consisted of fusible

deposit.

In 5 cases the whole calculus consisted of phos

phate of ammonia and magnesia.

In these 52 cases out of 233, the calculus might have been lessened by the injection of dilute acids, and in 12 out of these the whole calculus might have been removed. This supposes however that in all these cases the calculi were in the bladder, and not in the kidneys, on which there is no satisfactory historical evidence.

In addition to these 52 cases there are 6 calculi which consist entirely of urate of ammonia and fusible deposit, and 19 in which fusible and urate of ammonia form the outside layer. In these cases, most probably, any acid injection would dissolve the fusible and decompose the urate of ammonia, and thus disintegrate the calculus. So that altogether in 75 out of 233 a solvent might have assisted in the removal, although in 18 only out of 233,

or

about 1 in 13, could the calculus have been entirely removed. For this Sir B. Brodie has shown dilute nitric acid sufficient. Perhaps at some future time lactic acid, which possesses a peculiar power of dissolving the phosphates, may be found even more rapidly efficacious.

APPENDIX.

SINCE the foregoing paper was written, I have been examining a small collection of between twenty and thirty calculi, chiefly removed by Mr. Cæsar Hawkins.

The first of these was a small calculus about the size of a large nut, which had been divided: the section showed a large nucleus with a few thin layers around it. The nucleus was dirty yellow, semitransparent, crystalline, irregularly radiated, and rather soft. The external layers were much harder, whiter, and less crystalline. The nucleus entirely disappeared with heat, giving a most disagreeable and peculiar smell; it dissolved with little difficulty in nitric acid with effervescence, and when evaporated afterwards to dryness, it left a black residue, which ammonia did not alter. A little of the powder from the nucleus was boiled with water in a test tube to this a drop or two of a solution of acetate of lead was added, and then an excess of caustic potash.

:

On boiling, this mixture became in a few minutes jet black. This proof of the presence of sulphur was conclusive as to the nucleus of this calculus being cystine.

The layers exterior to this nucleus contained no cystine; when treated with nitric acid they gave evidence of uric acid, which was combined with ammonia, being soluble in water, and evolving ammonia when heated with liquor potassæ. By heat, a considerable residue was left, which dissolved with effervescence in dilute acids, and afterwards gave a larger precipitate of lime. By long-continued heat an alkaline ash remained. Hence the external part

of the cut surface consisted of urate of ammonia and oxalate of lime.

The external surface of this calculus also appeared to consist of two substances, a white crystalline superficial part, and an inferior brownish yellow substance. The first consisted of crystals of oxalate of lime, the second of urate of ammonia and oxalate of lime.

Hence the cystine deposit continued for a considerable time, and was succeeded by urate of ammonia and oxalate of lime for a comparatively short time, and this was followed for a still shorter period by oxalate of lime alone.

Through the kindness of Mr. Hawkins I am able to give the history of this calculus, which he removed from James Roberts, 6 years old, at the Asylum for the Recovery of Health, in 1828. The boy had suffered from symptoms of calculus for

four years. The pain occasionally was so great that he was held up by his feet to give him relief. The operation was performed on the 25th of October, and the wound healed on the 6th of December. He returned to Cornwall, and nothing has since been heard of him.

This case proves the existence of a deposit of cystine so early as two years of age. It has not as yet been found in a patient of more than 47 years. Of the ten cases recorded by Dr. Prout, eight occurred between 47 and puberty. One before 12 years of age, and one before the patient was five years old.