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"When burnt, dissolved in pure hydrochloric acid, evaporated to dryness, redissolved in water, and tested with ferroprussiate of potash, no Prussian blue was formed: hence none of the colouring matter of the blood is present in this calculus."



Communicated By THOMAS HODGKIN, M.I).

READ FEBRUARY 28th, 1843.

It has long been known that the arteries are very liable to a disease in which a soft matter of diverse consistency, and usually of a brown, yellowish, or white colour, forms between the internal and middle coats; that this matter, though it has been variously denominated, has often received the epithets atheromatous and steatomatous; that it is sometimes a forerunner of partial thinning and destruction of the internal membrane, a frequent concomitant of thickening and corrugation of this tunic, and of ossification of the vessels. And it is as well known that their inner surface is extremely subject to small opaque white or buff-coloured spots, either isolated, grouped together in irregular patches, arranged in streaks, or so diffused as to present merely a clouded or speckled appearance. These spots are seated in the internal membrane, occasionally confined to the epithelium, often occupying the whole thickness of the coat, and extending thence to the middle one, in which stage of the disease the matter first mentioned will generally be found in more or less quantity between the two coats.

But although the frequency of these diseased conditions has made them familiar to the pathologist, and their connection with the cause of aneurism, and with the obstruction and obliteration of arteries, must have occurred to almost every one who has investigated the diseases of the blood vessels, I am not aware that the morbid products in question have yet been made the subject of precise inquiry.

In the matter between the inner and middle coats, the following constituents may be seen with the aid of the microscope, namely :—transparent crystalline plates of a pearly lustre; oily globules of variable magnitude, the largest of which are free, while the smaller spherules are often aggregated together in the form of round, oval, or shapeless corpuscles; small earthy concretions; and a multitude of very minute particles, frequently forming a kind of granular ground for the other objects. When the matter is thick, they will be all best seen after diluting it with water or weak acetic acid. Sometimes the small oily globules form a larger corpuscle by mere aggregation; occasionally they adhere to an albuminous flake; while in the large rounded or oval corpuscles, the little oily particles are usually connected together by a very fine granular precipitate. The appearances just described are represented in the figures 1 and 2.

The fatty matter is often sufficiently abundant to give a greasy stain to paper when dried on it by heat.

The crystals are of cholesterine, as I learn from Dr. Davy, who kindly undertook the examination of different specimens of them which I sent to him for the purpose. Besides the cholesterine, he found that the hot alcoholic solution deposited on cooling a few needle-crystals, which had the properties of cholesteric acid. He also detected in the matter a notable quantity of oleine, with a smaller proportion of margarine, a little albumen, and earth of bones.

I have examined a great number of arteries affected with the disease, and never failed to detect oily globules and an abundance of cholesterine in the matter. Pursuing the instructions of Dr. Davy, I have also repeatedly dried it, as well as the middle coat of the vessel, extracted the fatty materials by boiling alcohol, observed the crystals of cholesterine and some margarine deposited as the solution cooled, and obtained the oleine by evaporating the spirit.

There is almost always atrophy and discoloration of those parts of the middle coat of the artery which happen to be near to the accumulated fatty matter; and more or less thinning and weakness of this coat appear to be often, if not generally, associated with thickening and corrugation of the internal membrane. On these points Dr. Davy has made similar observations.*

In the spots of the inner membrane, the bright fatty globules are very characteristic, and often plentiful enough to give a greasy stain to paper when dried on it by heat. Their most common arrangement is shown in figures 3 and 4. Crystals of cholesterine are frequently seen in the spots, though not so commonly as in the more abundant deposit between the internal and middle coats; and the speckled inner tunic generally yields a little cholesterine to hot alcohol.

There is seldom ossification of the arteries, or thickening and puckering of their lining membrane, without the formation of fatty matter between this coat and the middle one, as well as in the substance of both of them. The matter may be so scanty as only to be found after a careful search; but even in this case, in any places where the middle coat has become thinned or discoloured, or the connection between it and the lining membrane loosened, and a little of the soft opaque matter can be scraped off for examination, the cholesterine and oily particles may be detected with the aid of the microscope; and so it is also with even the smallest quantity of the opaque liquid or pulpy matter which may be found in contact with the bony plates.

* Researches, Physiological and Anatomical, Lond. 1839, vol. i. p. 372 & 436.

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