The arteries are subject to many diseases, to in flammation and its terminations, adhesion, sup puration, ulceration and gangrene; to aneurism; to the internal or serous coat being found of a deep red colour with a deposition of coagulable lymph; to a deposition of atheromatous matter, a thickened pulpy substance like steatoma, a cartilaginous mat ter, and a calcareous matter between their coats; they are also involved in inflammation and other diseases of contiguous structures. Of these the calcareous deposit is much the most frequent, and is the most common cause of aneurism.
Aneurism, which is derived from aveuguvre, to di late, consists of several species, the true, false, in ternal mixed, varicose, and aneurism by anastomo sis. True aneurism, strictly speaking, is a circular or uniform dilatation of the three coats of an arte ry, and is commonly met with in the aorta, accom panied with thickening of the serous and muscular coats, and depositions of calcareous matter on the exterior surface of the serous, and not unfrequently athcromatous pulp between that and the muscular tunics. Some systematic writers describe two va rieties of this, a circumscribed and a diffused true aneurism, which appears superfluous. A partial or lateral dilatation of the three coats of the aorta is also sometimes seen constituting another variety of true aneurism. The true aneurism of the majority of systematic writers on surgery consists in a rup ture of the serous and muscular coats, with a dis tension of the cellular, which effect is produced by the brittleness of the serous tunic being studded with calcareous depositions, by inflammation and ulceration or mortification, by partial dilatation from debility or undue impulsion, by absorption in consequence of some diseased spot of a blackish colour and slightly inflamed, by a deposition of co agulated blood, or by a separation of the serous coat from over exertion plugging up the vessel. The first of these is found to be the most common cause. When the three coats arc either at once ruptured in consequence of a wound, or by the cel lular tunic in this true aneurism also bursting, and the blood is diffused in the cellular substance in the contiguity condensing it into a cyst, the disease is styled circumscribed false aneurism, to distin guish it from that in which the blood is more ex tensively diffused in the cellular tissue even of the muscles, and which is named diffused false aneu rism. When the muscular coat only is ruptured,
and the serous protruded through it, the affection is denominated internal mixed aneurism. Varicose aneurism consists in a communication being estab lished between an artery and a vein from a wound. Aneurism by anastomosis arises from a congeries of arteries and veins forming a vascular tumour.
Aneurisms occur more frequently in men than iu women, the former sex being more subject to those occurring in their extremities, the latter to those in the trunk; and in many individuals it is a con stitutional disease. Aneurism occurs most com monly between thirty and forty years of age, and is said to attack the irritable, the passionate, the glutton, the drunkard, the debauched, the syphilitic, the mercurial, and the rheumatic. Coachmen, post-boys, postilions, soldiers, particularly dra goons, sailors, porters, labourers, and miners, are said to he most subject to it. These classes of in dividuals, by indulging in such vices, appear to dispose their arteries either to calcareous deposi tions or to a brittle condition, so that in the violent exertions which occur in their labours, these ves sels rupture and form aneurism, in consequence of the circulation being propelled at such periods with greater force than the artery has powers of resistance; but even in the ordinary circulation of such constitutions, if an artery be weakened, it is unable to resist the momentum of the blood, and therefore, gradually yields and dilates. Violent shocks or contusions, forcible pressure on arteries, the reiterated bruising of parts, the force employed in reducing luxated joints, the violence of falls, fractures and wounds, are also causes of aneurism. The largest artery, the aorta, is most subject to this disease, the next in frequency is the femoral, and its continuation the popliteal, the third is the inguinal, the fourth the subclavian and axillary, and the fifth the carotid. The smaller series of arteries, the radial, ulnar, and tibial, are seldom attacked, with the exception of the temporal, which from being selected in arteriotomy is exceedingly subject to aneurism. The nutritious arteries of the tibia have been found affected with aneurism. The reasons of this order are very palpable, being chiefly consequent on the impetus of the blood, and the deficiency or delicacy of the adventitious tunics, together with the deficiency of support by the con tiguous structures.