The calculous diathesis is so imperfectly known, and calculus of the bladder so rare a disease, that little has been attempted to prevent it. As stone, however, when once extracted, will sometimes recur, preventives, at that time, should be employed. In this class, general tonics will be found useful; and if there is any whose action is more particularly directed to the kidneys, these should be preferred. The uva ursi has been supposed to have this effect, and it may be em-cd with the decoction of the bark: at the same time, a mild diet, with every plan that will dilute the urine, without stimulating the urinary vessels. The free use of watery fluids; some of the diuretic vegetables; fruit, of which Linnaeus seems to prefer strawberries; are proper, though with an admixture of mild animal food. The acidulous soda water will be an useful drink. If the danger is apparently more urgent, the use of the bitters may be occasionally intermitted; and soap, with lone water, given for six weeks or two months, when the bitters may be again resumed. The patient should never suffer the urine to stagnate, but use himself to discharge it at stated times in the day and night, which will soon bring on the habit of doing so, whatever the quantity in the bladder may be. This, however, must not be too often practised. Once in the night, and three times in the course of the day, at least, the discharge should be encouraged. If his life is a sedentary one, it should be more frequent:

A calculus, however, at last shows itself by symptoms somewhat equivocal, differing, however, according to its seat. Gravelly concretions in the kidneys, which seem to consist almost exclusively of the uric acid, we must consider under the article Nephritis; and a stone occurring in the ureter cannot be easily mistaken. Acrid matter in the urine, a coagulum of blood, or gluten, will sometimes occasion violent pain, which will be mistaken for a fit of stone, and nothing can ascertain the complaint but the catheter, unless the offending cause should be discharged. An abscess of the prostate, or in the rectum, pressing on the bladder, has been said also to imitate the pain of a calculus; yet, as these are easily ascertained by an examination per rectum, the error can neither be long continued nor dangerous.

When a calculus exists in the bladder, it produces pain chiefly by paroxysms. There are intervals, often long ones, of the most perfect ease, but the paroxysms are extremely severe. These are relieved by emollient oily clysters, followed by opiates in the form of clyster, and by the mouth; the doses of which must be such as to meet the pain, whatever quantity may be required. We may notice, in this place, that the proportion of opium which is employed in relieving the pain, has no effect on the constitution in general; it is the excess of this dose which is felt.

The disease, however, remains; and it must then be considered whether the operation should be hazarded, or the solution of the stone attempted by internal medicines. The operation, though severe, is not peculiarly dangerous; yet, to attempt it on exhausted arthritic constitutions would be highly improper: if firm, no period of life is an obstacle. Another consideration must, however, stop us. We do not remove by the operation the disposition to form sane; and the disease has been known to recur. It does not, however, always return; and, within our observation, it has not returned in the greater number of instances. We remember an observation of Mr. Justamond, that the operation does not succeed if the patient has previously used lithon-triptics. But this we have not found supported by experience. If, therefore, the constitution of the calculous patient is firm, if the paroxysms are frequent and severe, if lithontriptics are not found in three or four months to greatly relieve, the operation is advisable. See Lithotomy.

Many, however, will not submit; and, in all, we think lithontriptics should be tried; for, though we have no decisive evidence of their dissolving stone, they greatly mitigate the pain, render the paroxysms more distant, as well as more mild. It has been seen from the experiments of Fourcroy, that almost every ingredient in calculi is dissolved by the caustic alkali; and various experiments have shown that the whole calculus yields to its powers. Lime water has been found also a solvent of calculus out of the body; and on these our hopes have chiefly rested. It is obvious, however, that what is taken by the mouth, has not only a circuitous route to reach the bladder, but is subject to many chemical changes; nor, indeed, are there many wellauthenticated facts of the urine being so changed, as to become a menstruum for the stone. Almost the only instance, except the case of Dr. Newcombe, recorded by Dr. Whytt, is that of Mr. Holme. Yet, though it may not be so accumulated in the urine as to render it an active solvent, it may destroy the animal oxide in it, or prevent its tendency to concretion; and it may have sufficient powers to soften the surface of the stone so as to lessen the irritation, and, of course, the spasmodic symptoms, which are its consequence. It is, we believe, an incontrovertible fact, that, where the stone has been unchanged, the paroxysms of, pain have been greatly mitigated; and, to lessen pains so violently excruciating, is surely an object of no little importance.

Lime was long known as a solvent of stone, and different methods were employed to administer it with safety. One. of these plans fell into the hands of Mrs. Joanna Steevens, daughter of a gentleman of a respectable family in Berkshire, and her success occasioned a considerable anxiety to discover the secret: At last, parliament bought it for 5000l. after different trials had been made of it with advantage. In many instances, stones, which had been sensibly felt, were no longer to be discovered; and, as the same persons were examined by surgeons, men of the greatest skill and eminence, both before and after the exhibition of the medicines, it is fair to conclude that in some instances they were dissolved, though we have recorded the singular mode which, in one case, occasioned the deception. Mrs. Steevens, it is said, first gave the calcined' egg-shells only, but finding these produce costiveness, she added soap. In time she rendered her process more complicated, adding snails burnt to blackness, a decoction of camomile flowers, parsley, sweet fennel, and the greater burdock. When we consider the effects of bitters, we shall not perhaps think, with Dr. Hartley, these additions to have been wholly useless. It is singular, however, that the egg shells, though calcined, were exposed to the air till reduced to a fine powder. No one seems to have carefully examined them in this state; and it is only presumed that they retained some portion of the caustic acrimony. Various other ingredients were confessedly used as disguises.