artery was exposed to the extent of about 1 inches, and raised upon the handle of a scalpel. Then with a percussion-hammer it was struck several times pretty smartly, so as to bruise the vessel considerably, between the handle of the scalpel and the hammer. The artery was afterwards replaced in its position, and the wound sewed up. The right femoral artery was now laid bare for at least 11 inches, and four ligatures of the texture of shoemaker's thread were placed around it. The two upper were tied tightly in a single knot, within one-fourth of an inch of each other; the lowest was tied in the same way about ths of an inch below the second one. The third ligature was tied round the artery in a double knot, but so that the loop thus formed was larger than the artery, and consequently did not compress the latter at all. The three tightly tied ligatures were afterwards removed, but the third one was left. The wound was now sewed up.

March 19th. The same dog was again put under the influence of ether, and operated upon in the following manner:-The left common carotid artery was laid bare to the extent of about 1 inches, raised from its position by a ligature passed round it, and then pinched firmly several times between the blades of a dissecting forceps, so that the walls of the vessel were thoroughly bruised. The artery was then replaced in position, and the wound sewed up. March 22nd, half-past nine A.M.-The dog was poisoned with hydrocyanic acid.

Autopsy. Both wounds in the leg were partially open, their edges thickened and callous-looking, emphysematous and infiltrated with a dirty serous-looking fluid. The right femoral artery and vein and crural nerve were very firmly matted together to the extent of about an inch or rather more-so much so, that it was only by cutting that they could be separated from one another and from the surrounding parts. The ligature which had been left on the artery was still there, and around it was a small quantity of dirty pus. On cutting open the artery, a little fluid blood was found in its cavity, but no coagula at all, and on the blood being washed away by a gentle stream of water, the internal coat of the artery was seen to be quite normal in colour and appearance, except at the three points where the ligatures had been tightly tied, where three reddish lines were seen corresponding to the ruptured inner coats. The walls of the artery at the injured part, to the extent of about three-fourths of an inch, were very much thickened, and consequently much more rigid than natural, so that it was with difficulty that the vessel could be held open to enable me to inspect the state of the intima; the walls of the vessel had at this part a great tendency to roll inwards. Owing to the thickening of the arterial tunics, the calibre of the vessel was at this point considerably diminished. The left femoral artery and vein and crural nerve were on a level with the wound, matted together, and strongly adherent to the surrounding parts for the extent of about an inch, but not so firmly as the vessels of the right side. On cutting open the left femoral from below, the cavity was seen to contain some fluid blood, but no coagula of any kind, and on washing away the blood

with a gentle stream of water, the internal surface of the intima was seen to be perfectly normal in colour and appearance. For the space of from one-half to three-fourths of an inch, corresponding to where the vessel had been bruised, the walls of the artery were much thickened-at least to twice their ordinary thickness-and so rigid that it was with difficulty on this side also that the divided walls could be held asunder, so as to enable me to inspect the intima. The wound in the neck was not gaping, but on removing the ligatures, the edges separated, and showed a large cavity with walls of a brownishred colour, and smeared with a dirty pus. On cutting down upon the left carotid artery, it was found to be slightly more adherent than usual to the surrounding parts, to the extent of about three-fourths of an inch. Over the space of about half an inch, where the artery had been pinched between the blades of the forceps, the external surface of the vessel was slightly livid, so as to indicate where the bruising had been. On cutting it open, some fluid blood was found in its interior, but no coagula whatever. On washing away the blood with a little water, over the space of about half an inch, corresponding to the external slightly livid portion, the intima had several bright-red ecchymosed spots distributed over its internal surface, and the inner and middle coats were ruptured irregularly in several places, and not all round the artery. There was, however, no inversion of the edges of the ruptured coats.

Thus we see that when, in the preceding experiments, the inner and middle coats of the arteries operated upon were ruptured close together, and all round the vessel once in two, twice in three, and once in four places; in not one of the cases was there any inversion or coiling up of the ruptured coats into the tube of the vessel, nor any coagulation of the blood in or consequent obstruction of the artery.

Dr. Jones operated upon horses, but also upon dogs, and in both kinds of animals the results of his experiments were, as has been shown, very different from mine. It is difficult to explain this apparent contradiction. All that I can do is to lay a detailed account of my own experiments before the profession, and leave their right appreciation to the judgment of each individual.

The conclusions to be drawn from my experiments are the following:

1. When the internal and middle coats of a healthy artery of a dead human subject or of a dead animal are ruptured, either regularly all round the vessel, or irregularly at different places, there occurs, in by far the majority of cases, no inversion or coiling up of the cut edges of the tunics, but these remain quite on a level with the other portions of the surface of the intima.

2. Rupture of the inner coats of the arteries of healthy living dogs in the same way as described in the preceding paragraph is also, for the most part, unattended with any coiling up of the edges of the divided inner coats

3. Rupture of the intima and media of the arteries of healthy living

dogs-whether in one line all round the vessel, or in several circular lines closely apposed to each other, or irregularly at different parts of the interior of the artery-is not of itself sufficient to cause coagulation of the blood in, and consequent obstruction of, the vessel at the injured part.

4. Inflammation of the arterial walls, of such a degree as to cause great thickening of the same, and consequently a considerable diminution in the calibre of the vessel, is insufficient of itself to cause coagulation of the blood in, and consequent obstruction of, the artery at the point inflamed.

I may also venture to observe that it remains yet to be proved that there exists any disease of the arterial coats producing such an alteration in the texture and physical properties of the inner tunics as to cause the same, when ruptured, to curl up into the tube, and, by mechanically occluding the canal, induce coagulation of the blood at the injured part.

The objection to these conclusions may be made, that there are many well-authenticated cases recorded in medical literature of arterial obstruction caused by rupture of the inner and middle coats of the vessel. Of the fact that obstruction of the arteries did occur, of course there can be no doubt, but the alleged cause of the obstruction must, in my opinion, be called in question. In all such cases, save one, that I have been able to find recorded, the obstruction seems to me quite as easily explained on the embolic theory of coagula sent from a distance and becoming impacted in the arterial canal, as on the hypothesis of rupture of the inner coats of the vessel.

Thus Dr. Oke of Southampton, in the 'Provincial Medical Journal,' vol. iv. p. 51, 1842, relates a very interesting case of arterial obstruction, which he attributes to "spontaneous rupture of the internal coats of the artery, and the projection of its edges into the tube;" and in the third volume of the Transactions of the Medico-Chirurgical Society of Edinburgh, 1829,' there is a paper by Mr. Turner on Obstruction of the Canals of the Arteries, describing ten cases, the obstructing cause in all of which is referred to "rupture of the internal coats of the arteries."

For a detailed account of the above cases reference must be made to the original papers, as it would occupy too much space to reproduce them here. Suffice it to say that all the eleven above-mentioned cases, with the exception of the third and fourth, of Mr. Turner, are evidently cases of embolus, where the affected vessels have been suddenly obstructed by coagula or cardiac vegetations conveyed to them from a distance.

In cases of the latter kind it must be observed,

1. That it by no means follows that because there are no physical signs of cardiac disease, therefore the case cannot be one of embolus, for coagula may form, as they pretty frequently do, in the left auricular appendage of the heart, pieces of them may afterwards become loosened thence and conveyed into some distant arterial canal; or again, the blood may coagulate in the pouch of a cardiac aneurism,

and portions of the coagulum may become separated and propelled into some of the peripheral arteries without their having been necessarily any symptoms of valvular disease of the heart in the person affected.

2. That more than one artery of the body usually becomes stopped up, and these vessels are generally affected at different times, e.g., the main artery of one arm of a person may all of a sudden become obstructed, and then in a few days afterwards precisely the same symptoms may seize upon one of the legs, as in Mr. Turner's first case.

3. The obstruction caused by an embolus generally occurs at the part of an artery where the calibre of the vessel suddenly diminishesviz., at the point of division into two or more branches.

4. When a piece of blood-coagulum or any other foreign body becomes impacted all of a sudden in an artery, the irritation of the same sets up inflammation of the walls of the vessel, the latter become thickened, adherent to the surrounding parts, and the intima dies and separates from the media. That the death of the intima is in such cases a consequence of the irritation of the foreign body, is shown by the fact of this tunic being usually destroyed only at the obstructed point, and being in the rest of its extent of quite healthy appearance.

Now, in all the above nine cases, which seem to me quite easily explicable on the embolic theory, the symptoms of obstruction came on suddenly; in most of them there were well-marked pectoral symptoms, either before or after the stoppage of the circulation in the affected arteries, thus showing that there was in all probability cardiac derangement, although perhaps not valvular disease to be detected by the ear during life; in five the obliteration took place in either more than one vessel or in more than one part of the same vessel, and in the two cases where there was a post-mortem examination of the affected vessels, the obstructions were found at points of division of the vessels into smaller branches, and in these two cases, everywhere but at the affected portions of the vessels, the intima was perfectly healthy in appearance, except in Turner's first case, where at one part of the popliteal artery there was a small crucial fissure or laceration of the internal coats, but where, nevertheless, there was no coagulation of the blood in, or consequent obstruction of, the vessel.

The third case mentioned by Mr. Turner appears to me to be one of embolus also, although I must confess that it is by no means so evidently so as the nine before mentioned. As the case is somewhat remarkable, I shall detail it here at length. It was under the care of Dr. Abercrombie, of Edinburgh.

"The patient, a man named John Anderson, aged sixty-three, first complained on 6th November of a fixed pain about the top of the right thigh and groin, and after a day or two the thigh became numbed and weak, gangrene of the whole limb came on, and the man died on the 13th November.

"On examination of the body after death, there was found a great quantity of a dark-coloured fluid effused into the limb, and the muscles were universally dark and gangrenous behind the peritoneum; on the right side of the abdomen there was a large gangrenous cavity, containing much dark-coloured fluid and ill-conditioned pus. The femoral artery being laid open, there was found disease of the inner coats in several places. These were soft and separated at

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various points from the outer coat, so as to lie across the area of the vessel like valves. One of them was about a third down the thigh, and there were others less remarkable. On slitting open the external iliac artery, the inner coats were found soft and thick, and at one place completely lacerated in the whole circumference of the artery, and separated from the external coat for nearly an inch and a half, the portion thus separated having fallen down and coiled up, so as completely to obstruct the canal of the artery nearly at the place where it passes under Poupart's ligament. Between this and the origin of the internal iliac artery there were considerable lacerations of the inner coats. In two places they were slightly detached from the outer coat, and their edges projected into the tube of the vessel. Above the obstruction at the lower part of the iliac, produced by the more extensive laceration, there was a coagulum of blood in the artery. The aorta was in several places diseased, its internal surface ulcerated, and the inner coat partially separated. In some of the smaller branches of the arteries in the pelvis there was ossification, but none in the right iliac artery, where this singular disease was situated. The left iliac artery appeared sound. No other diseased appearances were detected. It is obvious that the obstruction to the circulation was produced by the torn and detached internal coats of the artery."

The description of the post-mortem appearances in this case is certainly very imperfect, so that the following remarks upon them are quite open to correction.

It is said that the inner coats of the femoral artery were in several places soft, and separated at various points from the outer coat, so as to lie across the area of the vessel like valves. There is no mention, however, of any blood-coagula being found in these portions of the affected vessel; now this must surely have been the case if, during life, the internal tunics lay like valves across its cavity, unless coagula had been there some time previously and had softened down, the artery meanwhile becoming obstructed higher up, and so the blood prevented gaining access again to the vessel after the breaking down of the first coagula. Neither is the structure of the blood-coagulum situated above the obstruction at the lower part of the iliac artery described, so as to enable one to form an opinion as to whether its nucleus was constituted by a thrombus or any foreign body conveyed from a distance, or whether the coagulum had formed entirely at the spot itself. Then the aorta was in several places diseased, and its internal surface ulcerated. Now, there is nothing improbable in the supposition that bloodcoagula may have formed at the diseased portion of the aorta, pieces of them have subsequently become loosened thence, and been propelled into, and have obstructed, the femoral and iliac arteries in several places and at different periods, the gangrene and separation from the adventitia of the internal coats being a secondary affection caused by the irritation of the emboli. Under such circumstances, the coagula in the most distant parts of the artery from the centre would, of course, have been the oldest, and would perhaps have had time to soften and break down, while those higher up nearer the centre, being of more recent date, would have been found still entire; which indeed were just the appearances described by Dr. Abercrombie.

In Mr. Turner's fourth case, which came under his own observation,