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 diarrhoea 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

is decreased; the chlorides are decreased; and as unnatural constituents there are albumen, casts of tubes, epithelial cells, and mucus. These conditions of the renal secretion are those common during the absence of pyrexial disturbance dependent on local inflammatory lesions. In pyrexial states the urine may become highly coloured, and may even give an abundant proportion of urea.*

CAUSE AND CAUSATION OF URÆMIC COMA.

We know as a primary fact that uræmic coma is the result of arrested secretion of urine.

The proposition is proved by the direct experiment performed on inferior animals, of arresting the urinary secretion, either by removal of the kidneys, by ligature of the renal vessels, or by division of the renal nerves. When any one of these experiments is carefully conducted, the symptoms and pathology of uræmia are produced with as much accuracy of detail as can be desired.

The symptoms caused by suppression of the function of the kidney (I speak from my own experimental observation conducted on dogs) vary somewhat according to the degree of the operation. If both kidneys be removed from action, uræmia is an inevitable fact. If one kidney only be suppressed in function, uræmia in the majority of cases is again the fact; but occasionally there is this exception, that the

*For the most perfect history extant on the condition of the urine in acute and chronic uræmia, I refer the reader to Dr. Parkes's work On the Urine, chap. v, pp. 376-394.

animal recovers without the occurrence of any serious mischief. Granting the accession of uræmic symptoms after either operation, they are not usually presented for ten or twelve hours. The first symptom then observed is a rigor, which subsiding leaves the subject sleepy and motionless. For some time, however, he may be roused without much difficulty; but on the occasion of all such attempts he is, as a general rule, disposed to vomit. He will refuse food, but will often partake freely of water. Dogs in this state never express anger nor sign of acute pain. At intervals there are paroxysms of convulsion, but very subdued in kind, and apparently occurring during periods of oblivion. After the development of the first rigors, the temperature of the body rises; I have seen the thermometer in the mouth rise, for example, six degrees beyond that at which it stood before the operation. The respiration, so soon as the somnolency is established, becomes markedly irregular; it will vary ten or even twenty in number per minute; at the same time, it rarely exceeds fifty inspirations and expirations per minute. Corresponding with this irregularity of respiration, the action of the heart is equally unbalanced. There may be a variation of so many as twenty and from that to thirty beats per minute; and here too, as in the human subject, this peculiarity may be marked, that the irregularity shall extend over a long space, and so observed shall become very obvious, while per beat it shall not stand out at all distinctly. If these symptoms have been induced by the removal of