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Ammonia, nor Nitrate of Potash injected into the blood of animals proves speedily fatal, unless the kidneys be previously extirpated (Hammond). If, however, the quantity of urea injected be very large, death does take place. Stannius, on the contrary, states that urea injected into the blood is harmless; and Petroof has injected a large quantity into the blood without causing coma. Dr. Hammond has shown that the urine, as a whole, is more poisonous than a simple solution of urea. has proved most conclusively that Frerichs' notion, that the urea became decomposed into Carbonate of Ammonia, is erroneous; and Johnson, Richardson, and others are of the same opinion. Hoppe finds that in uræmia the extractives are increased to three times, and the Creatine to five times the normal amount. In many cases of severe uræmia there is, however, no urea to be detected in the blood, and various hypotheses have been, from time to time, advanced to explain the fact, but none of them are entirely satisfactory. The extractives are very much increased in some cases, and their relation to the albumen rises from 5:100 to 40: 100, according to Schotten. It is possible that in some cases in which a large quantity of urea is detected, the formation of this substance has been going on actively for some time, and has accumulated in the blood or has even passed, after its passage into the uriniferous tube, directly into the blood, by the rupture of the upper part of the tube and adjacent capillary or capillaries, or through the lymphatics, its escape into the pelvis of the kidney having been prevented. In those cases of death from uræmic coma in which no urea is to be detected in the blood, it is most likely that the secreting structure of the liver, and probably also that of the kidney, has ceased to be active altogether, and that urinary constituents are not even formed. In such a case it is probable that death results from the accumulation in the blood of those materials which it is the duty of the kidneys to separate, or from the presence of compounds resulting from the decomposition of these. In considering this question, it must be borne in mind, not only that the renal disease has gradually advanced, and the kidneys, perhaps, have become almost inefficient, but that most important altera

tions have been slowly taking place in the blood, and in the action and reaction of the various organs supplied by it. Many tissues in the organism must be secondarily affected, and must have gradually become much altered in structure. At present we are but very imperfectly acquainted with the normal changes occurring in the blood, or with the consequences immediately resulting to the tissues, especially the nervous system, from the retention of certain excrementitious matters, independently of urea; and we know very little of the remote or immediate effects resulting from excrementitious substances not being formed at all. The question is a more difficult one than it appears at first sight, and requires more searching chemical and microscopical investigation than it has yet received. One writer on this subject concludes a very elaborate essay thus: “Enfin, cette altération chimique du sang est encore mal définie, et la science attend sur ce point de nouvelles recherches." (“De l'Urémie," Thèse, par Alfred Fournier, 1863.) Possibly "uræmia" may depend not upon the presence of one single constituent of the urine only, as urea, in the blood, but rather on the accumulation of a number of products resulting from the disintegration of tissue which ought to be separated by the kidneys. This is the general conclusion arrived at by one of the more recent writers on the subject, M. Rommelaere, whose memoir contains records of valuable original observations. ("De la Pathogénie des Symptômes Urémiques," par Dr. W. Rommelaere. Bruxelles: Henri Manceaux, 20, Rue de l'Etuve.) I shall have to refer again to uræmia, under the head of acute inflammation of the kidneys.

But whatever difference of opinion there may be as to the exact nature of the uræmic state and the mode as well as the order of the causation of the several pathological phenomena which accompany it, or of which it is a consequence, there can be none whatever as to the proper treatment of the condition. It is here that the principle of rapid elimination must be promptly acted upon and actively carried out. Free purgation must be brought about, and aided by free diaphoresis, if this can be excited. Diuresis cannot be regarded as advantageous in

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these cases, for the kidneys being in a state of inflammation and the capillary vessels congested, the organs must not be stimulated to increased action, but rather assisted to rest for a time, their work being thrown upon other organs, especially the bowels and the skin, until the kidneys are restored to their normal state, when free diuresis often takes place, and many substances which have been accumulating for some time are excreted, and the patient soon becomes convalescent. This subject will be further considered when the treatment of acute inflammation of the kidneys is discussed.

Ammonia. Numerous experiments seem to show that in health a small quantity of ammonia escapes in the urine. Neubauer has conclusively proved that certain ammoniacal salts pass through the organism, and may be detected in the urine unchanged. Ammonia, as is well known, is very easily produced and in large quantity, by the decomposition of the urea. It is, however, almost certain that a small quantity may under some circumstances pass into the urine from the blood.

In many bladder cases the quantity of ammonia present in the urine is often so considerable that it may be smelled all over the room in which the patient lies, but it arises in some of these from the decomposition of the urea after the urine has left the bladder, and in others it is decomposed even while it yet remains in this viscus, not in consequence of its formation in and removal from the blood, but from the chemical decomposition of the urea. It is doubtful whether a large amount of ammonia under any circumstances can accumulate in the blood afterwards to be excreted in the urine, as it is probable that, if formed, it would escape more rapidly from the lungs or from the intestinal canal than from the kidneys.

Uric Acid and Urates are present in varying proportion in healthy urine, but in disease a large increase is very frequently observed. The proportion in health is about half a grain in 1000 of urine, and is often less than 3 per cent. Uric acid and urates usually form urinary deposits, either from existing in too large a proportion to be dissolved in the urine when cold, or, as is probably the case in the majority of instances, from the devel

opment of an acid in the urine, which causes them to be precipitated from their solutions. But occasionally much more than the normal amount is held in solution. Whether there is really more uric acid formed and excreted than in health may be ascertained by mixing the urine passed during twenty-four hours and estimating the uric acid in a small quantity, and calculating the amount in the whole.

In many acute febrile conditions, the proportion of uric acid is increased, and the period of resolution of the inflammation is marked by diminished frequency of the pulse and respiration, by a fall in the temperature, by free perspiration, and by a very abundant deposit of urates. In health; not more than from 5 to 8 grains of uric acid are excreted in twenty-four hours; but, in some acute diseases, the proportion may amount to 20 grains. In a case of fever, Dr. Parkes found that 17.28 grains of uric acid were excreted in twenty-four hours. Dr. Sansom has estimated the quantity of uric acid in 1000 grains of the morning urine in health and several cases of disease. The results are as follows:

Urate of soda is easily caused to yield crystals of uric acid. If the amorphous urate deposit be merely dissolved in warm water or by warming the urine, the urate may become decomposed. As the solution cools, crystals of uric acid are deposited. In some cases, the quantity of uric acid held in solution is so great that, upon the addition of a drop of nitric acid to the urine, an abundant amorphous precipitate, exactly resembling albumen, is at once formed. Such precipitate has many times been mistaken for albumen, and, even if examined under the microscope immediately after it is formed, its nature cannot be made out. If,

however, it be allowed to stand for some time, the amorphous particles gradually increase in size, and assume the well-known crystalline form of uric acid. The instances in which I have met with urine exhibiting these characters have for the most part been cases of liver disease. Although the reaction of the urine is acid, no precipitate takes place upon the application of heat, by which fact urine of this character may at once be distinguished from albuminous urine.

In some cases, although the urine be perfectly clear or only slightly opalescent, with no distinct deposit, an unusually large quantity of uric acid or urates, or both, may be held in solution. Upon the addition of an acid the uric acid is set free in abundance. Such cases require to be treated upon the same principles as those in which visible deposits of uric acid and urates are frequent. Patients having urine of the character above indicated often take, for weeks together, considerable doses of alkali with advantage, but persons adopting this treatment should always be cautioned against continuing the alkali for too long a time without an interval, during which a tonic mode of treatment is adopted or medicine of every kind withheld.

The presence of an increased quantity of uric acid in the urine shows that more of this substance or its salts is being excreted than in health. A large proportion of the uric acid resulting from the disintegration of albuminous substances taken as food, or forming constituents of the blood or tissues, combines with ammonia, soda, or lime, forming urates of these bases, which are excreted in the urine. In cases where considerable excess of nitrogenous matters are taken in the food, much of the excess passes away as uric acid.

In gout, the presence of uric acid in the blood has been shown to be constant by Dr. Garrod, who considers that in this condition "the kidneys lose, to some extent, their power of excreting uric acid, although they eliminate urea, as in health.” In many cases of gout, although there is no albumen in the urine, that series of changes which ends in structural disease has already commenced, and the normal power of elimination interfered with. During the attack of gout there is less uric acid in the