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The following paper is the result of an analysis of a collection of calculi, most of which were presented by Sir B. Brodie to St. George's Hospital. The collection now consists of 233 divided calculi, not including any duplicates, and 9 undivided, these last having some peculiarity in form. The analysis was begun in 1831 by Dr. Prout, who examined 24 specimens, and from these as well as from the remainder which I have analysed, I shall endeavour first to show that when the urates are deposited there is reason to suppose that little or no free acid can exist in the urine, and that consequently alkalies, however useful they may be in other respects, are not requisite in such cases to remove acidity. When we find an acid reaction on test paper, it is by no means a

true conclusion that therefore free acids exist, and alkalies must be given to remedy this state of disordered secretion. As far as we yet know, the truth appears to be, that free acid is not usually present, and that consequently alkalies are generally not required to neutralize acidity in the urine.

I will secondly point out in what proportion of cases in this museum acid injections might have dissolved or partially removed the calculus

Of those calculi which have been divided,

46 are simple, that is, consisting throughout of one substance.

40 are compound, consisting throughout of a mixture of two or more substances.

147 are alternating.
Of these alternating calculi,
83 have a simple nucleus.
58 have a compound nucleus.

If, instead of looking at the calculi from this point of view, we examine them for the purpose of seeing how often the same substance forms either a whole calculus, or occurs in a well-marked layer, we shall find that in this collection there are at least 450 distinct deposits. These I have arranged in the accompanying Table, from which it will be seen that 135 times uric acid occurs either alone or

mixed with other substances.
222 urate of ammonia, ditto.
163 oxalate of lime, ditto.
139 the phosphates, ditto.

urate of ammonia with oxalate of

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Table of 233 Calculi examined. These consisted of at least 462 well-marked Layers, of which 450 may be thus arranged.

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of Twelve Layers not included in the above Table,

10 contained Carbonates

2 Uric Acid and Phosphates (Dr. Prout). 12

In order that a deposit of urate of ammonia or of uric acid, with urate of ammonia, may take place, it is necessary that an excess of urate of ammonia, as compared with the quantity of water, should exist in the urine ; yet this is not the case as regards a deposit of uric acid alone. It will be shown that for uric acid to be precipitated, no other unnatural state need be present except that of some free acid passing in excess out of the system. In this, perhaps, we may find a partial explanation of the frequent occurrence of uric acid calculi.

Urate of ammonia appears to be increased in the urine from very slight causes. The very frequent occurrence of this deposit in the state of health rendered it very probable that this substance would be often found as a constituent of calculi. Since Dr. Prout first proved its existence, other chemists have repeatedly recognized it, and this collection is not singular in the number of calculi which contain urate of ammonia.

Oxalate of lime appears from the above Table to exist with uric acid, with urate of ammonia and with the phosphates. It occurs 80 times in 450, with urate of ammonia forming a distinct deposit. As these substances occur together so often in calculi, so must they frequently be met with in the same sediment: that is, there must be a certain diathesis, in which urate of ammonia is formed at the same time with oxalate of lime. By means of the microscope this can be shown to be true. And in the red deposit of rheumatism and of indigestion


I have found octohedral crystals of oxalate of lime, sometimes in large quantities. This mixed diathesis I hope soon to bring again before this Society.

In order to arrive at the state of the secretion when the substances in the above Table were deposited, we must consider, with Dr. Prout, that urate of ammonia exists in the urine in the state of health. The rapid deposit of this substance when urine is evaporated under the air pump over sulphuric acid, and the change which ensues if even carbonic acid is first passed through the liquid, admits of no other conclusion than that uric acid exists in healthy urine combined with ammonia. And as we find by experiment that all acids, even down to carbonic acid, are capable of causing a deposit of uric acid, and that when acids are added in small quantities an equivalent quantity of uric acid is deposited, and if much acid is present, that all the uric acid is thrown down, and that no urate of ammonia is left undecomposed; it appears that free acid and urate of ammonia cannot exist for any length of time in the same solution. We find, moreover, that urine which reddens litmus, when cool, deposits urate of ammonia, and after being again heated and cooled, again deposits the same substance; and that however often this be repeated, no decomposition takes place, no uric acid crystals can be detected by the microscope; whence we must conclude that whilst urate of ammonia only is deposited, no free acid can be present, although litmus paper may be reddened.

We may make satisfactory experiments on this

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