PHOSPHATES.

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

50

17

16

56

Nature of deposit on Calculus Nature of deposit on Calculus Deposit when Oxalate of Deposit when no Oxalate of

when there is a tendency
to an excess of urates, in
proportion to the water.

when Oxalate of Lime is
formed, and the urates are
in excess.

Lime only is formed, and
no urates in excess.

Of Twelve Layers not included in the above Table,

Lime is formed, and no
urates are in excess, and
no free acid is present.

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

subject in the living body. To a patient who passes urate of ammonia, we may give acid medicines and cause a deposit of uric acid in its place, whilst litmus paper will be far more strongly reddened than it previously was.

For the above reasons, therefore, it seems most probable that when uric acid alone is deposited, much free acid must have been thrown out by the kidneys, and that thus all the urate of ammonia, which would otherwise have been present, must have been decomposed. If we wish to know how often in calculous complaints this highly acid state of secretion occurred, we must not only observe how often whole calculi consist of uric acid, but how often whole layers of this substance occur. This appears

from the Table to have been 97 times in 450.

It was above stated that when little acid was added to urine or taken by a patient subject to a deposit of urate of ammonia, that substance was only partly decomposed; and the conclusion which must be drawn from this seems to be, that when urate of ammonia is found mixed with uric acid, but little free acid is secreted by the kidneys. Such a mixture was found to occur in 38 layers. Hence in 38 states out of 450, but little free acid was thrown off in the urine.

When we find urate of ammonia alone, without any uric acid, forming a calculus or layer, we must consider that no free acid was removed by the kidneys, although the secretion may have been acid to test paper.

The presence of the phosphates in a deposit generally implies a neutral or alkaline state of the urine. If such be the case, and the presence of uric acid implies an acid state from free acid, it would follow that uric acid and the phosphates must exist very rarely in the same deposit. When the calculus has consisted chiefly of the phosphates, I have not once found uric acid to exist with it. When traces of this acid have been present, ċareful examination showed it was in combination with some base.

And when the calculus consisted chiefly of uric acid, the small ash which sometimes remains will rarely be found to consist of the phosphates.

In the above Table the phosphates occur 139 times. Hence 139 times in 450 the urine must have been neutral or alkaline to test paper.

If then phosphates indicate neutrality or alkalescence, and uric acid indicates free acid in the urine, we may conclude that the deposit of oxalate of lime, as it occurs in the above Table with uric acid, with urate of ammonia and with the phosphates, is independent of acidity and alkalescence, and that its presence in a layer does not indicate any particular state of the secretion.

Now, as such layer implies a certain state of the urinary secretion, the 450 layers may be taken to represent 450 states of the urine.

139 of these were neutral or alkaline, as so many

times the phosphates are found to occur.

311 were feebly or strongly acid to test paper.