"The alternating calculus, as the name imports, may consist of different layers of any of the preceding species. Hence its general appearance, texture, &c. will depend entirely on the composition, and may be very varied. Most commonly it is composed of a lithic acid or mulberry nucleus, and an external crust of the fusible calculus. In some rare instances, it is composed of laminæ of all three of these substances, and sometimes of even more—the mixed phosphates still continuing to constitute the external crust. This species of calculus often acquires a very large size and is very common.—Chemical characters. The chemical characters must of course vary with the composition; and as the different substances of which it is composed must almost certainly be some of the preceding, the nature of the different laminæ can be readily ascertained by what has been already stated," p. 79, et seq.
In the chapter on the comparative prevalency of different forms of urinary deposite; and the order of their succession, we have a number of important facts and observations. Dr. Prout calculates, from the data collected by him, that about one-third of the urinary calculi which occur, are of the lithic acid species, and that another third are formed on a nucleus of this acid. Hence, "we may assert," says he, "that at least two-thirds of the whole number of calculi originate from lithic acid; that is to say, if a lithic acid nucleus had not been formed and detained in the bladder, two persons at least out of three, who suffer from calculus, would have never been troubled with that affection. This is a most important fact, and deserves to be constantly borne in mind."
The relative prevalency of the oxalate of lime calculus is very various. The average proportion, as determined by Dr. Prout is about one in seven. Of the calculi, examined by Mr. Brande, 1 in 25 was of the mulberry species; while in the Norwich and Guy's Hospital collections, the proportion is about 1 in 4. In the Bristol collection, one-sixth of the whole, was composed of oxalate of lime, nearly pure; while, including all the concretions containing more or less of the oxalate, the proportion was nearly one-half! This great disparity in the proportional frequency of this calculus in different districts of England, clearly shows the great influence of local causes, in determining the character of urinary concretions.
From a careful observation of the order of deposition of different species of calculous matter, Dr. Prout has been enabled to deduce the following general law; "that, in urinary calculi, a decided deposition of the mixed phosphates is not followed by other depositions." So that it would appear, that a redundancy in the earthy phosphates is the last link in the chain of diseased alterations, to which the urinary secretion is liable.
In the third chapter, under the second subdivision of functional urinary diseases, Dr. Prout describes the lithic acid diathesis, and communicates several important original observations. After remarking that the dyspeptic are particularly predisposed to lithic acid deposites, he enumerates, as exciting causes of this species of gravel, 1st. Errors in diet; 2nd. Unusual or unnatural exercise of the body or mind, particularly after eating, and the want of proper exercise at all other times; and 3d. Debilitating causes. Under errors of diet, an unusually heavy meal, especially of animal food, and the use of heavy, unfermented bread, or compact, hard-boiled, fat dumplings or puddings, salted and dried meats, acescent fruits, malt liquors, and acescent wines, are enumerated as particularly hurtful in the lithic acid diathesis.
The above remarks refer to the amorphous lithic deposites, consisting of lithate of ammonia. In regard to crystallized sediments, or, more properly speaking, gravel, our author makes the following remarks:
"Crystallized sediments, or red gravel, consist of lithic acid, nearly pure. Lithic acid, as has been before stated, exists in a state of combination in healthy urine; and in such a proportion, as to be held in a state of solution at all ordinary temperatures. Sometimes, however, a free acid is generated by the kidneys, which precipitates the lithic acid in the pure crystallized state we see it—a phenomenon easily imitated artificially, as is well known, by the addition of a few drops of any acid to healthy urine. The precipitation of crystallized lithic acid does not, therefore, necessarily indicate an excess of lithic acid in the urine, but the presence only of some free acid in that fluid; though such an excess does, for the most part, exist in this form of disease, as will be shown hereafter. With respect to the nature of the precipitating acid, it is probably not always the same. Most generally it appears to be the muriatic, sometimes the phosphoric or sulphuric, and occasionally other acids. In general, however, it is to be understood, as noticed elsewhere, that when the mineral acids are present in excess, these are the immediate cause of the preternatural acidity in the urine, and consequently of the precipitation of the lithic acid. The stronger acids act by decomposing saline compounds, into which destructible acids, such as the lactic acid, &c. enter, and setting them free. Hence the immediate cause of the deposition of lithic acid gravel is generally a destructible acid of very weak powers: even, perhaps, in some instances, the carbonic acid. When the urine contains a free acid, it is commonly more transparent than usual, and of a bright copper colour." p. 112.
The treatment recommended by Dr. Prout in this species of gravel is as follows: First, a strict attention to diet, avoiding the hurtful articles already enumerated. Secondly, the use of alkaline remedies; but those must not be depended upon, without the aid of other means, more especially of alteratives and purgatives. Accordingly we are informed that
"The pil. submur. hydrarg. comp., or a pill composed of the pil. hydrarg. and pulv. antimonialis, may be taken twice or thrice a week at bed time, and followed up the next morning by an active dose of the sub-sulphate of magnesia, or a mixture of Rochelle salts and magnesia, or carbonate of soda. A little of either of these compounds may be also taken twice or thrice in the day, so as to keep the urine constantly neutral or alkaline, and the bowels freely open; or gr. x to xx of magnesia may be taken for the same purpose in a glass of soda water, as often as it may be found necessary."
In the chapter on the mulberry, or oxalate of lime diathesis, Dr. Prout gives a number of cases, from which he draws the following conclusions: