Cases of dissecting aneurism, or that form of aneurismal affection in which the sac is situated between the coats of the vessel / by Thomas Bevill Peacock.

  • Thomas Bevill Peacock
Date:
[1843]
Catalogue details

Licence: Public Domain Mark

Credit: Cases of dissecting aneurism, or that form of aneurismal affection in which the sac is situated between the coats of the vessel / by Thomas Bevill Peacock. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    external coat became at once distended, not, however, in the form of a distinct tumour, but throughout the whole course of the ves- sel from the pipe to the ligature at its origin. The parts being re- moved from the body and dissected, the fissure was found to oc- cupy one-third of the circumference of the vessel, and to be situ- ated at its front, and about the middle of the descending portion. It penetrated through a part of the middle coat, and from this point a separation of the layers of that tunic was produced, extending above to the ligature on the origin of the artery, and downwards to that on the pipe. It was situated in the middle coat, and involved at the lower part, two-thirds of the circumference of the vessel be- incr there bounded by the origins of the intercostal arteries. At the ascending and transverse portions of the aorta, the coats were separated only at the front of the vessel. In the innominata and the left carotid arteries, the separation ceased at their origin, but ad- vanced about three-quarters of an inch along the left subclavian, surrounded its whole circle, and then, as in the other two vessels, re- opened into its canal. The layer of the middle coat separated in connection with the external coat at the posterior extremity of the artery was extremely thin, but increased in thickness towards the origin of the vessel, till in the ascending portion it was fully half- a line in width. Both the internal coats were, throughout the course of the vessel, free from any appearance of disease. From this experiment, which has been frequently repeated and variously modified with a similar result, we are, I conceive, Avar- ranted in concluding with Dr Davy* that the coats of the aorta are, in a healthy state, capable of extreme distension before giving way, and, consequently, that the rupture of the internal coats of the vessel, which constitutes the first step in the formation of a dis- secting aneurism, must be ascribed to their being rendered lacer- ableby disease ; and secowrfZ?/, that, after the occurrence of a fissure penetrating the substance of the middle coat, that membrane will readily admit the blood to effect a separation of its laminse. In this respect the experiment corresponds with that related by Dr Pennock. From experiments-|- of a similar kind instituted on the aorta after entire rupture of its internal coats, it appears that, though the cellular membrane between the external and middle 'tunics still more readily allows of separation along the course of the vessel, yet that, even where most distinct, the external coat docs not alone possess sufiicient density to resist the pressure of the extravasated fluid, and hence it is most probable that the sac of the dissecting aneurism will be found to occupy the jaminse of the middle coat, a layer of that membrane being in all cases united to the separated external coat,—an inference which is supported by the facts,that, in each of the three recent cases which • Ucsearches, Physiological and Anatomical, Vol. i. p. 446. t For a fuller account of these experiments see the Ed. and Lond. Monthly Jour- nal for October 1843.
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