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Aneurysm.

Abnormal arterial dilatation.

A soft tumor, arising from the widening up or dilatation of an artery.

Tumor produced by the dilation of an artery.

A swelling in the coat of an artery.

The disease of an artery when it expands and sometimes bursts, permitting the blood to spread about in the surrounding tissues.

Properly, Aneurism signifies a tumour, produced by the dilatation of an artery; but it has been extended to various lesions of arteries, as well as to dilatations of the heart. There are various kinds of aneurism. The following are the chief: I. When the blood, which forms the tumour, is enclosed within the dilated coats of the artery. This is the TRUE ANEURISM, Aneurys'ma verum, Hernia Arteria'rum, (F.) Anevrysme vrai. II. When the blood has escaped from the opened artery, it is called SPURIOUS or FALSE ANEURISM. The latter is divided into three varieties: 1. Diffused False Aneurism, (F.), which occurs immediately after the division or rupture of an artery, and consists of an extravasation of blood into the areolar texture of the part. 2. Circumscribed False Aneurism, (F.) in which the blood issues from the vessel some time after the receipt of the wound, and forms itself a sac in the neighbouring areolar membrane. 3. An'eurism by Anastomo'sis, Var'icose or Circoid An'eurism, Phlebarteriodial'ysis, Aneurys'ma veno'so-arterio'sum, A. varico'sim, (F.) which arises from the simultaneous wounding of an artery and vein ;-the arterial blood passing into the vein, and producing a varicose state of it. III. MIXED ANEURISM, is that which arises from the dilatation of one or two of the coats, with division or rupture of the other Some authors have made two varieties of this: 1. Mixed external Aneurism, where the internal and middle coats are ruptured, and the areolar is dilated. 2. Mixed internal Aneurism, in which the internal coat is dilated, and protrudes, like a hernial sac, through the ruptured middle and outer coats. This variety has been called Aneurys'ma Her'niam Arte'rice sistens. Aneurisms have been termed traumat'ic or exog"enous, and spontaneous, according as they may have been caused by a wound, or have originated spontaneously. The latter, when originating from lesions of the inner coats of arteries, have been termed endog"enous. They have also been divided into internal and external. The internal aneurisms are situate in the great splanchnic cavities, and occur in the heart and great vessels of the chest, abdomen, &c. Their diagnosis is difficult, and they are often inaccessible to surgical treatment. The external aneurisms are situate at the exterior of the head, neck, and limbs, and are distinctly pulsatory. Aneurisms, especially the internal, may be combated by a debilitant treatment, on the plan of Valsalva, which consists in repeated bloodletting, with food enough merely to support life. In external aneurism, the artery can be obliterated. This is usually done by applying a ligature above the aneurismal tumour.

A tumor formed by localized dilatation of an artery through which blood circulates. Such tumors are distinguished by their expansive pulsation with each systole of the heart, by a thrill to be felt in them on palpation, and by a bruit heard on auscultation. As they increase in size they produce absorption of adjacent structures and give rise to distressing symptoms by their pressure on nerves. Their final tendency is to burst and, if a large artery is the seat of the tumor, to cause death. They are classed as: (1.) true arterial a. and (2.) arteriovenous a. A pulsating arterial hematoma, even though its walls are not formed by the wall of an artery must be classified with aneurisms.

n. [Greek] A soft, pulsating tumour, arising from the dilatation or rupture of the coats of an artery.

A disease of the arteries, in which they become excessively dilated.