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in solution by the presence of an alkaline body, which is liberated as an ammonia on the addition of a displacing agent.

In a case recorded by F. Simon, the serum exhibited a remarkable milk-white turbidity. This colour, which was not caused by fat in a state of suspension, was found to depend on the presence of numerous minute solid granules, which on collection and inquiry were found to be insoluble in alcohol and ether, but soluble in dilute acetic acid, from which they were separable by ferrocyanide of potassium. Hence Simon concluded that they were particles of fibrine.

The same experimentalist found hæmatoglobulin more abundant in the hæmatin in cases of uræmia, than in ordinary cases. It varied from 8 to 9.5 per cent.

The amount of urea in the blood is increased. This fact, asserted by Christison, Simon, and all the earlier writers, but disputed by other succeeding authors, is now satisfactorily proved. The experiments of Hammond on the increase of urea in dogs, after extirpation of the kidneys, remove all doubt. In one of his carefully conducted inquiries, 100 grammes of blood removed from the jugular vein before extirpation of the kidneys yielded 0.026 gramme of urea : whereas, twenty-four hours after extirpation, 100 grammes of blood from the same vein yielded 0.083 gramme of urea.

From these peculiarities of blood, we may pass to the pathology of other structures. Effusions are common during uræmia: they must be so, for, in condi

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tions where the functions of the kidney are suppressed, and albumen is an excrete, not only is there accumulation of water in the tissues, but there is decreased specific gravity of blood, which, in proportion as it exists, induces exudation by incapacitating that fluid from eliminating its water. This result of uræmia-exudation-occurs in divers parts of the organism ; in the cellular tissue, in the serous cavities, in the bronchial mucous tract, in the ventricles of the brain. With the mere serum thrown out, pseudo-plastic material is sometimes admixed; and, after death from uræmic coma, these exudative products may constitute a marked feature in the morbid representations. They are to be looked upon as sequences; and, although they may materially have influenced the course of a case, their secondary character should invariably be recognised by the philosophical student.

Whether effusion exist or not in uræmia, there is always more or less of congestion of the vascular organs. In the earlier stages this frequently leads to diseased states of special organs, inflammatory in appearance. In later stages the congestion becomes universal; for, as we shall see by and by, in comparing the mode of death in uræmia with asphyxia, that while the congestion commencing at the kidney is for a time partial only, extending to the lungs it is reflected through the whole of the soft tissues. Hence, after death from uræmic coma, we almost invariably find congestive enlargement of the liver and spleen, intense congestion of the lungs, with distension of the sinuses of the cerebral membranes, and congestion of the minute vessels of the brain itself. For this same reason the muscles are often dark and filled with blood, and the inner surface of the arterial system is deeply stained.

It is worthy, too, of special remembrance, that the congestive condition above described may extend to the alimentary mucous surface in any part of its tract.

This fact, of which I have given one illustration (vide pp. 134-5), is important, inasmuch as the congestion of the alimentary tube is usually followed by exudation of serous fluid containing urea. Mixing now with the secretions natural to the canal, the urea is transformed partially or altogether into carbonate of ammonia, which acting in turn as an irritant, produces, when present in excess, distinct gastro-enterite with diarrhea and vomiting as symptoms, and an inflamed mucous membrane as the visible morbid upshot. Thus in the train of acute uræmia we may have all the results of an irritant poison. We may have gastro-intestinal inflammation, or peritoneal effusion, or both combined. We may have congestion of lung, pleural exudation ; cerebral congestion, ventricular effusion; deep staining of the endocardial membrane, and equally dark staining of muscular fibre. We may, I say, have all these obvious lesions, or we may have none of them; for if, on the one hand, the suppression of the kidney be immediate and perfect, death may take place purely from a rapid disorganisation of the blood, owing to accumulation of water with the urea ; or if the arrest of the renal secretion be slow, so that time is given for the exudation of serum containing urea, the decomposition of the urea is the result, and of that decomposition all the lesions which have been pointed out are necessary sequelæ.

It would lead me into a subject foreign somewhat to this essay, to discuss at any length the morbid conditions of the kidney with which uræmia is related. Some authors have endeavoured to connect uræmia with special lesions of the kidney. My own experience is to the effect, that uræmia may succeed on any acute or chronic obstruction in the renal organs. After scarlet fever, in addition to the congestion, the condition met with, perhaps in all cases, is exudation into the tubules and epithelial desquamation. In other cases, atrophy is the morbid representation ; in a third and more numerous class, enlargement with granular, fatty, or waxy degeneration. In a fourth modification (of which the case of the boy J. S., whose history is given at pp. 142-4, is a type), the kidney may present no sufficient lesion to account for the symptoms and their consequences. In these examples it is probable that there is some latent and undiscovered lesion of the nervous centres or of the renal nerves, by which lesion the secreting power of the kidney is reduced or estranged; for we know that all the effects of uræmia are producible by simple division of the renal nerves.

The pathology of the urine varies with the state of the uræmic patient. There may be periods when persons who are the subject of renal obstructive dis

ease have their urine free of abnormal constituents, but during uræmic coma, on which only this essay treats, there is invariably a large presence of albumen. In this respect, both in acute and chronic cases the rule is the same; but in other respects there may be distinctions, not only between one case and another, but in the same case at different periods. For example, in acute cases, such as those which occur early in scarlatina, the urine is albuminous, although to external appearance it is pyrexial, i. e. high coloured, small in quantity, and charged with red sediment; from ignoring this circumstance of pyrexial albuminous urine, scarlatinal uræmia is often overlooked until it is represented by deep and unmistakable coma.

With the presence of albumen in the urine in these stages, there may be a decreased amount of urea ; but this is not an absolute rule, for occasionally the urea is temporarily increased. There is a deficiency of chlorides; and, sometimes in addition to the foreign element albumen, there are blood itself, fibrine, casts of tubes, and mucus. As the disease advances, the albumen increases in quantity and the urea is decreased, but without any absolute relationship in respect to the proportion of either substance.

In cases where there has been long standing kidney-disease, with uræmic coma supervening, the quantity of urine is usually scanty; the appearance of the fluid closely resembles thin beef-tea, or thin white of egg emulsion ; the reaction is neutral or very feebly acid ; the amount of urea and uric acid

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