As to sex, females, owing to their less active life, are but little affected with aneurism, the proportion being one to seven, as compared to males.
Spontaneous aneurism is usually due to degeneration of the artery-wall caused by atheroma or adipose infiltration. As a result, the artery is unable to con tract during the cardiac diastole, and its diminished resistance to the pressure of the. blood caused the vascular walls to gradually dilate. As atheroma presents itself chiefly during middle life, while physical use of the system is still violent, this class of aneurism is most frequently met with in people between thirty and forty years of age. Inflammatory changes are also considered as a prolific cause.
Aneurism is solely a consequence of alterations of the arterial walls, particu larly arteritis. Alcoholism accounts for great frequency of this affection in cer tain countries. Localization in arterial coats depends upon the more or less ad vanced degree of sclerosis or atheroma. Duplaix (Des An6vrysmes et de leur Traitement, '95).
The old theory that degeneration of the wall of the artery always precedes aneurism of any vessel is the true one. toss of vascular tone can scarcely be accepted as a sufficient cause. A. Me , Phedran (Can. Pract., Aug., '95).
Aneurism of the abdominal aorta noted in a boy. 9 years of age, who had been repeatedly the subject of rheuma tism. There was also atheroma of the aorta, and in two places there were be ginning aneurisms of the arch. The aneurism of the abdominal aorta was as large as a golf-ball. It was at the divi sion of the common iliac arteries. R. K. Aitken (Brit. Med. Jour., June 25, '98).
Syphilis is a common etiological factor.
Importance of syphilitic arteriosclero sis in the production of aneurisms in sisted upon. Of twenty-eight cases syph ilis found to exist in twelve. Heiberg (La Semaine Medicale, July 27, '92).
Of nineteen patients 47 per cent. had had syphilis, all under fifty years of age. This illustrates the relation of precocious arteriosclerosis and syphilis. Fraenkel (Med. Record, X. Y., Nov. 17, '94).
Among European residents of Japan aneurisms of the abdominal and thoracic aorta are very frequent; syphilis is very common. Eldridge (N. Y. Med. Jour., Feb. 10, '94).
Syphilis found to be a possible cause in one hundred and sixty-six eases out of two hundred and forty. In twenty
eight of the one hundred and sixty-six cases syphilitic lesions were present. The greatest frequency of aneurisms occurs between five and ten years after syphi litic infection.
In the great majority of eases aneu risms due to syphilis cannot be distin guished from aneurisms due to other causes, nor are any special pathological lesions present. Differentiation by treat ment is not reliable. Etienne (Ann. de Dermatologie, vol. viii, p. 1, '97).
The term "dissecting aneurism" has been applied to a form in which, the inner walls of the aorta or one of the large arteries having ruptured, the outer coats remain intact, the blood dissect ing a passage between the layers of the middle coat. There are altogether about two hundred cases of this condition re corded, and in by far the larger number of these death evidently occurred either immediately or within a few- hours, most frequently by the blood forcing its way into the ascending aorta and thence into the pericardial sac. Only in a small percentage of the cases was compensa tion established and the dissecting chan nel repaired either by the development of secondary openings into the vessel or by the organization of the blood, which, after escaping between the walls, became clotted. There are singularly few cases on record of this last mode of repair; it is more common to find that. where death is not the direct result of the con dition, the dissecting channel gains an endothelium, a channel being formed, opening above and below into the aorta or one of the larger arteries, and resem bling the primitive vessel so closely that it is not to be wondered at that some of the earlier cases of the condition were described as congenital abnormalities. (Adanii.) Dissecting aneurisms may be due, in the old, to atheromatous change; in the young to congenital malformation of the central organs of the circulation; some times, also, to traumatism. Hypertrophy of the heart, especially in its left half, is often present. Traces of peri- or endo carditis are often to be noted. The rent in the inner coat sometimes precedes, sometimes follows, the distension. A number of rents may occur in the same subject.