hour. The bladder contained bloody urine. The right kidney weighed 90 grs.; the left, 170 grs.

Exp. 11. The left renal vein being exposed, in a small healthy rabbit, the artery was seen to pass obliquely behind it, rendering it very difficult to isolate the former vessel. A thread was passed around both, and tied so as to enclose both within a loose loop. Eight hours afterwards, the animal was alive and well. At the end of twenty-four hours, I found it dead and cold. The left kidney was much enlarged; it was enveloped in a distinct cyst, apparently formed of the surrounding cellular tissue, which had been infiltrated with blood and lymph. Except at one point, where the kidney had been slightly scratched, there was no adhesion between that organ and its investing membrane; in fact, they were separated from each other by a small quantity of serous fluid. After reflecting this tunic, an inner one (which I imagined to be the proper capsule) appeared, and, like the former, could be detached from the surface of the gland: thereby proving satisfactorily the real existence of a second membrane. The bladder contained about a drachm of clear urine, which was moderately but distinctly albuminous.

Exp. 12. A precisely similar operation was performed on a rabbit of the same size, the vein alone being included in the loop; it died at the end of two days and a half. The left kidney was surrounded by a cyst similar to that met with in the

last experiment; it adhered slightly at one or two points to the capsule; the latter could be stripped off the kidney, and the separate existence of the two membranes thus manifested. The external surface of the gland presented three or four white spots, resembling those of incipient suppuration or softening. The urine in the bladder was of a faint reddish tinge, and was very highly albuminous.

CLASS II.-Designed to illustrate the Peculiarities of Arterial Determination.

A.-Removal of one kidney.

Four animals, of the same age and size, and in similar condition, were selected. The operation was performed at the same time on all of them, and the left kidney weighed at the time of its removal.

Exp. 1. The left kidney of a healthy young rabbit was removed, the vessels being previously tied; it died at the end of twenty-four hours, partly from the shock of the operation, and partly from peritonitis. The urine in the bladder was not albuminous. The left kidney, when removed, weighed 20 grs.; the right, 25 grs.

Exp. 2. A similar operation was performed. The animal appeared quite well at the end of the second day, when I poured some cold water over it, with the view of increasing the determination to the remaining kidney; it seemed unable to bear the shock, and died about the end of the third day. The urine contained no albumen; but on adding an ad

ditional quantity of nitric acid, there was a copious

precipitation of crystals of nitrate of urea.

kidney weighed 21 grs.; the right, 26 grs.

The left

Exp. 3. At the same period, after the operation, this animal was treated in the same manner as the last; it lived twelve hours longer than it. There was no albumen in the urine; nor did any deposit of urea take place on adding an equal quantity of nitric acid. The left kidney weighed 20 grs.; the right, 33 grs.

Exp. 4. Nine days and a half after the removal of its left kidney, this animal appeared quite well; it was then killed. The bladder contained a small quantity of urine, which yielded a faint cloudiness when treated with nitric acid. The left kidney weighed 21 grs. ; the right, 50 grs.

Exp. 5. The left kidney of a middle-sized strong rabbit was removed, and the animal killed at the end of nine days. The left kidney was unfortunately not weighed; the right was evidently much enlarged. The urine in the bladder was not albumi

nous.

B.-Ligature of the aorta, below the origin of the renal arteries.

Exp. 1. In a small weak rabbit, the abdominal aorta was tied, from an incision on the right side of the spine, which added to the difficulty, and, consequently, increased the shock of the operation. There was immediate and permanent paralysis of the hinder extremities. The animal died about ten

hours after the operation. Both kidneys appeared disproportionately large; each weighed 36 grs., and the tubular portion of each was reddened. The urine was tested with nitric acid. In a small quantity, there was no appearance of albumen; in a larger, some permanent opacity was produced, not removable by a slight excess of the acid.

Exp. 2. The aorta was tied, from an incision on the left side of the spine, in a middle-sized animal, in poor condition. There was immediate paraplegia, as in the last instance. Some hæmorrhage from the smaller vessels occurred. It was killed at the end of forty minutes. Both kidneys were of a lighter, or more rosy tint than natural; the tubular portion of each was reddened. The left weighed 4 grs. more than the right; probably from the lower origin of the left renal artery in this instance. The urine in the bladder was not albuminous.

C.-Ligature of the aorta, and removal of one kidney.

Exp. 1. The aorta of a middle-sized animal, in poor condition, being exposed by an incision in the left lumbar region, it was grasped by a spring forceps of moderate power. The obstruction to the flow of blood was complete, for the artery visibly enlarged above the point of compression. The animal was then liberated, and its hinder extremities were seen to be paralyzed, the useless limbs trailing after the rest of the body. The blades of the forceps were then separated, and carefully withdrawn, and

the animal almost instantly regained the power of moving its limbs. A thread was then passed beneath the aorta, and a knot tied at such a distance from the vessel as not to obstruct the flow of blood. The left kidney was now removed; it weighed 33 grs. On laying it open, the tubular portion was reddened, and on dissecting off the lining membrane of the pelvis, the primary arterial divisions beneath it were seen to be embedded in a quantity of clear lymph. The paralysis of the hinder extremities never returned. Four hours after the operation, it was alive, and hopping about. At the end of eighteen hours I found it dead. The right kidney weighed 35 grs. No lymph could be seen beneath the lining membrane of the pelvis. The bladder was distended with urine, which was not albuminous. The ligature hung quite loosely on the aorta, but some bloody lymph had been effused around it.

Exp. 2. In an animal of similar size to the last, and, like it, in very poor condition, the aorta, being exposed, was compressed by the same forceps, and the animal then set free. There was perfect paraplegia. The forceps being separated and withdrawn, it continued to lie in the same position, having its hinder extremities extended and useless, for a few seconds, and then suddenly sprung up with a bound, having perfectly regained the power of moving them. The aorta was then tied tightly, when the paralysis immediately returned, and continued unchanged till death. The left kidney being now removed, weighed 32 grs.; on laying it open, the redness of the tubu