those instances where the animal seemed to recover most speedily from the shock of the operation. B.-The obstruction of the renal vein being either incomplete or gradually effected. In 6 cases some venous hæmorrhage occurred from accidental or intentional laceration of the vein or its branches. In 2, the coats of the vessel were raised by a forceps, and a ligature so applied as to include only half the vein; leaving it at the moment pervious, though of diminished calibre. In 4, a thread was passed around the vein, and so tied as to enclose the latter within a loose loop; the vessel itself not being compressed by the ligature. The results will be most readily understood by a glance at the subjoined Table: The lymph found in the bladder, in one of these experiments (No. 4), was beautifully clear and pellucid. It was semi-fluid when first examined, but coagulated more firmly on exposure to the air. I am not aware that any other instance is recorded of the effusion of coagulating lymph, as the consequence of simple compression of the blood from venous obstruction. The quantity was so considerable, in this case, and the manifestation of its peculiar properties so decided, that there was not the least room for doubt. The physical condition of the blood in the vessels of this kidney must have been that of a fluid subjected to a continued moderate pressure: for, in consequence of a slight laceration of the vein, the blood could not be compressed beyond a certain degree, as it would then tend to ooze through the lateral opening. I have not succeeded in obtaining so much lymph in any subsequent experiment. It must ever be a very difficult point so to adjust the obstruction to the amount of impulse of the arterial blood as to maintain the requisite degree of compression, and no more, for a sufficient length of time. The two succeeding experiments confirm the accuracy of the explanation just given for in them the vein, being first tied tightly, was then punctured on the renal side of the ligature, so that a small jet of blood escaped. The organ being returned while in this condition, and the urine examined, at the end of an hour, both fibrinous and bloody coagula were found suspended in it. I think it not improbable that the blood, in these instances, escaped during the short interval that elapsed between the application of the ligature, and the puncture of the vein. For it will be remembered that, in a former case, blood was found in the urine at the end of three minutes and a half after the obstruction took place. Three of the above experiments (viz., the 8th, 11th, and 12th,) are related, not only for the illustration they afford, of the general principle here advocated, but from their tending to throw light upon the changes which these engorged organs would subsequently undergo. The circumstance of blood and albumen being present in the urine at so late a period as the third or fourth day after the operation, may be partially explained by the slow progress of bloody or fibrinous coagula along the ureter. At the same time, I think it is possible that some albumen may have been derived from the other kidney, in consequence of the increased determination to that organ. I cannot help thinking that the morbid appearances which these three engorged kidneys presented, viz., the formation of an exterior membrane or cyst, the appearance of white spots on the external surface of the organ, as in Experiment 12, and the more extensive disintegration met with in Experiment 8, were but the first of a series of changes which would finally have terminated in the softening down of the whole organ, and its conversion into a puriform mass. And it seems by no means improbable that when abscess of the kidney follows acute nephritis in the human subject, the formation of a bag of pus (as met with in post mortem examinations) takes place in a similar manner, and is preceded by simílar changes. An extended investigation of the changes which kidneys thus treated would finally undergo could not fail to throw important light on some of the secondary effects of inflammation. I shall now pass on to the second class of experiments, or those intended to illustrate the effects of an increased determination of blood to the vessels of a part previously healthy. It occurred to me, that if an increased flow of blood could be suddenly directed through any particular artery, the contractility of the smaller vessels would resist the rapid dilatation necessary for the free passage of the augmented quantity of fluid, and thus give rise to some obstruction. If any obstruction did take place, then both the conditions required to produce undue compression of the blood would co-exist, and some of its effects should be perceptible in the urine. CLASS II. A. I first attempted to accomplish this end in the case of the renal artery by removing one kidney, thinking that the physiological determination to the other might suffice. I repeated the experiment five times, chiefly in young and weak animals. The only constant result observed was a progressive increase in the weight of the remaining kidney. In one instance there were some slight traces of albumen in the urine. B.-—I then, in two small weak animals, tied the abdominal aorta below the origin of the renal arteries. In one instance the urine was slightly albumi nous. C.-As I did not by these measures, used singly, obtain very satisfactory results, I then wished to ascertain whether the simultaneous performance of both operations in animals of greater strength, would not, by the conjoint influence of the physical and physiological determination of blood to the remaining kidney, induce the presence of albuminous matters in its secretion. I performed seven experiments. The three first did not succeed; but a glance at the particulars of each, as given in the appendix, will, I think, suggest a satisfactory explanation of their failure. And any uncertainty which these negative results may have created as to the truth of the principle sought to be established in this part of the memoir, must be in a great measure removed by a careful perusal of the four last experiments. Thus in Exp. 4. The animal living 18 hours. 5. about 2 days. 6. 3 hours. 7. 2 hours. The urine contained blood, and the liquid portion It was highly albuminous. another of fibrine, and was highly albuminous. Blood and albumen. In removing the left kidney, care was taken to |