The gelatine accompanies almost every ingredient. It is the connecting medium of the other bodies mentioned; and is discovered by the fetid odour they exhale in the fire by forming carbon frothing in water, which thus acquires an annual smell, and in being precipitated by tanin.

We have given this abstract of the more important parts of M. Fourcroy's Memoir, not only to illustrate this subject by the latest chemical investigations, but to contrast it with the experiments of Dr. Pearson, perhaps to reconcile the discordant observations.

Dr. Pearson, neglecting the more violent methods of analysis, dissolved the calculi in caustic alkalis, and precipitated the dissolved portions by acids. The precipitate, when well washed and dried, was a light micaceous crystalline substance, consisting of nearly one-half of the original calculus. It is without smell or taste; scarcely soluble in cold water; does not unite to any alkaline substance, except when uncombined and caustic; it is at least not an acid. It cannot be sublimed without decomposition, and consequently cannot be the lithic or succinic acid. It docs not form a viscid solution with water, and consequently cannot be an animal mucilage. As in every trial it shows marks of an animal nature, Dr. Pearson styles it an animal oxide: according to this author, it is not putrescent or crystal-lizable, insoluble in cold water, producing a pink or a red residuum on evaporating its solution in nitrous acid. As an oxide he attempted to acidify it, but could only change it into ammonia and carbonic acid. He-found that when the nitric solution of this animal oxide was evaporated, the inflammation which took place owing to the production of nitrat of ammonia. The white, impalpable, tasteless, heavy powder left on the filter after the union of caustic soda, contained 175/300 of animal oxide; 96/300 of phosphat of lime; of ammonia, perhaps with phosphoric acid, mucilage, etc. 29/300. Dr. Pearson afterwards separated the lithic acid of Schcele, and found its properties wholly different from the animal oxide. On examining two hundred specimens of urinary calculi, thirty-two out of thirty-three contained this oxide, but its proportion varied usually from 0.40 to 0.70; and it sometimes was found in the exterior, sometimes in the interior, lamina;. It was not, however, found in the urinary concretions of any animal but man. It is found also in the human arthritic calculi, but not in the concretions of the teeth, stomach, intestines, lungs, or brain. This animal oxide Dr. Pearson calls uric oxide.

On comparing the experiments of these two chemists, it will, we think, be at once obvious, that the more operose and violent operations of the former produced new compounds; and, in confirmation of this idea, we must remark, that in every ingredient obtained by M. Fourcroy, animal matter was conspicuous: we have carefully pointed out its appearance in each. We may, therefore, safely conclude, that the animal oxide is the chief ingredient of the calculus, and that its component parts are the principles already described from the Annates du Museum National.

We should not, perhaps, wholly pass over the concretions of other animals; yet, not to distract the attention, we shall finish the subject of human calculi.

Notwithstanding the labour of the chemist, we are almost equally at a loss respecting the source of calculi, and what has been styled the diathesis calculosa. It is not hereditary: it is not acquired. No constitution is peculiarly subject to it; yet we think the fair complexions, with light hair and blue eyes, have been the most common victims. This may be fanciful; for if one often has been of this description, let it be recollected that not one of a million of this description has suffered from calculus. The remote causes, usually assigned, are equally without foundation. Hard water is certainly not a cause, for selenite is not an ingredient in calculi: wine does not occasion it, for the calculus does not able tartar. Cyder is equally harmless; and beer has been accused, only because, as a more general beverage, an unusual proportion of beer drinkers must be affected. It has been said, and generally believed, that a nucleus was only required to form a stone from the depositions of the urine; but gravel almost constantly occurs in the bladders of many persons, and yet no stone is formed. In short, it is one of those arcana which, after all our investigations, must still remain such. We know that our glass falls to the ground from gravity; and, though we know not the cause of gravity, we can, however, preserve it. We know not the source of calculi, but we can often mitigate their symptoms; relieve, perhaps, in some, though very rare, instances cure. If chemistry, however, does not assist us, we may perhaps draw some useful hints from analogy.

The connection of calculus with gout is well known; and the latter is certainly in a great degree depending on a weakened or disordered stomach. If animal matter is formed, but in a state not adapted for nutrition, it must be carried out of the body as an injurious substance, and it may be deposited on the kidneys or joints. We shall here be accused of inconsistency, and told that we are supporting the doctrine of morbid matter as a cause of gout. It is not, however, the cause, but the effect of the cause; in reality, the first in the chain of effects or symptoms. "In the constitution that has long suffered from the gout, it seems to be determined to the kidneys with the phosphoric acid retained in the early period of the paroxysm; and its concretion is assisted by the long confinement on the back, which the pain of gout often demands. In relaxed constitutions of the scrofulous kind, it may also be occasionally deposited in different parts, though the kidneys seem to yield it the most ready outlet. This appears to us a step, at least, towards the explanation of the cause. If fanciful, or unfounded, it has detained the reader only for a very short time.