ting the being my ass of the vascular
tel fome ads of the sorts to its

and the largest example of this variety
and all had been divided by a nar
extending over two-airds of the circumference
deal of extending the external cost into

fed felf between it and the middle fibrous cost, and de from oder, dongh more than half the elreum of the artery, from the seds of the sorte down to the common The enimal me was formed on one side by the exand on the other by the middle and internal costs. In one denied by Mr. Guchte, there was a fissure about half an in is eaten, by which the Mood escaped through the inner and doned separation of the middle and external coats, much dont de inches in length in the anterior part of ling sets. In the other example mentioned by Mr. Guthrie, ddle of the sorts were divided along half the cir ery dess rest, tastel opposite to the origin of the its, and as separation of the external and middle coats feeds from the rent to the origin of the aorta, and on the der spist oppe to the origin of the left subclavian, Los de fet vier who gave a minute description of this for, and it has been carefully investigated by Rokitansky,

In

who gives an account of eight cases which came under his own observation. These eight, together with two others, also referred to by Rokitansky viz, the one described by Laennec, and one by Dr. Stosch), the two loscribed by Guthrie, two by Mr. Smith, one by Nivet, and two by Goddard and Pennock, being seventeen in all, were, until lately, so far us I know, the only recorded examples of this kind of aneurism. almost all these examples the heart was diseased, and more especially its left side; in some instances there was dilatation with hypertrophy; in others dilatation with attenuation; and in many of them there were evident signs of steatomatous and calcareous deposits. According to Rokitansky, it sometimes commences by disease of the middle and internal conts, in which case the continuity of these coats is destroyed, and the separation of the external coat follows as a later effect; in other instances, it is the consequence of chronic inflammation of the external cont, which gives rise to separation of that cont, followed by rupture of the middle and internal coats, In the one set of cases he considers that the rupture precedes, in the other, that it follows, the separation.

6th. The late Mr. Shakelton described a kind of aneurism previously unnoticed, in which the blood had forced its way through the internal and middle coats, dissected the middle from the external cost to the extent of four inches, and then burst again into the channel of the artory, thus forming a new channel, which eventually superseded the old one, --the latter having been obliterated by the pressure of the tumour, In this case the aneurismal sac was formed by five conts on the one side, and the external cont on the other,

7th. In the body of a man about fifty years of age, who had not been supposed to be the subject of any disense, and who died very suddenly before any medical man had an opportunity of seeing him, I met with a singular variety of dissecting aneurism. In the arch of the norta, about three fourths of an inch to the left side of the origin of the left subclavian artery, there was a rent of the inner and middle coats from this rent to near the origin of the north on the carding side, and for upwards of an inch on the capillary side the external cont was sepa rated from the middle, round nearly two thirds of the circumference of the artery. There was an opening upwards of half an inch in diameter, by which the aneurism thus formed burst into the pulmonary artery, a little below the place where that vessel gives off its two branchen. norta was affected with steatomatous deposit in many places, and in this caso there were, beyond all doubt, patches of the same kind of degen vation in the pulmonary artery. There was very slight hypertrophy of the left side of the heart.

The

A true aneurism is invariably limited at first; that is, it is confined within a proper oyst; but, by rupture or ulceration, the cyst may give way, and the blood become diffused through the surrounding testuing in which ease the aneurism is said to be diffuse,

IV. Contents of the Nae. The contents of an anem bomal san are not the same at all periods; they vary consideraldy, nording to the bonth of time that has elapsed since the commencement of the discon Beat the pao contains only fluid blood, and in this stage, by excitin

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