XV. A Letter on the Differences in the Structure of Calculi, which arise from their being formed in different Parts of the urinary Passages; and on the Effects that are produced upon them, by the internal Use of solvent Medicines, from Mr. William Brande to Everard Home, Esq. F. R. S.

DEAR SIR,

Read, May 19, 1808.

HAVING availed myself of the opportunity you procured for me, of making a chemical examination of the calculi contained in the HUNTERIAN MUSEUM, as well as those in your own collection, I herewith send you an account of what I have done.

Should the observations appear to you to throw any new light upon the formation of calculi, I request that you will do me the honour of laying them before the ROYAL SOCIETY.

The collection which I have examined, is not only uncommonly large, but the greater part of the specimens have histories of the case annexed to them.

This circumstance enabled me not only to ascertain the situations in which the calculi were found, but likewise many of the circumstances attendant on their formation.

I have therefore endeavoured to form an arrangement upon these principles, with a view to render the subject more clear and perspicuous.

SECTION I.

Of Calculi formed in the Kidnies, and voided without having afterwards undergone any Change in the urinary Passages.

These have the following properties:

They are of a brownish yellow colour, sometimes of a grayish hue, which seems to arise from a small portion of dry mucus adhering to their surface.

They are entirely soluble in a solution of pure potash, and during their solution, they seldom emit an odour of ammonia. When heated to dryness, with nitric acid, the residuum is of a fine and permanent red colour.

When exposed to the action of the blow-pipe, they blacken and emit a strong odour of burning animal matter, very different from that of pure uric acid. This arises from a variable proportion of animal matter which they contain, and which occasions the loss in the analysis of these calculi. Its relative quantity is liable to much variation, as may be seen from the following statements.

A calculus from the kidney, weighing seven grains, was dissolved in a solution of pure potash. A quantity of muriatic acid (rather more than sufficient for the saturation of the potash) was added, and the precipitate of uric acid thus obtained weighed when dry 4,5 grains. No other substance, except animal matter, which was evident on attempting to obtain the muriate of potash, could be detected, consequently the composition of this calculus was as follows:

This is the largest proportion of animal matter which I have met with.

A small calculus from the kidney, weighing 3.7 grains, afforded by a like treatment 3.5 grains of uric acid, so that it was nearly a pure specimen of that substance.

The largest calculus of this kind which I have examined weighed seventeen grains; much larger ones have been found, but there is no evidence of their not having remained in the urinary passages for some considerable time. Thus Dr. HEBERDEN mentions one weighing twenty-eight grains.*

It often happens that the ingredients are not united together so as to form a calculus, but are voided in the state of a fine powder, commonly termed sand. This consists either of uric acid, or of the ammoniaco-magnesian phosphate, alone, or with the phosphate of lime.

I am induced to believe that the last mentioned substances, although the production of the kidnies, and held in solution, are never met with in a separate state till the urine has been at rest, and therefore, calculi from the kidnies are never composed of the phosphates.

In a few instances, calculi from the kidnies, composed of oxalate of lime, are voided; but this is a very rare occurrence : of three preserved in the HUNTERIAN Collection, two are

* Comment. on the Hist. and Cure of Diseases, 3d. edit. p. 88.