(1) Thrombosis and Embolism, (2) Obliteration, (3) Acute inflammation, (4) Chronic endarteritis or atheroma; (a) Causation and nature, (b) tissue changes, (c) effects on circulation, (5) Endarteritis obliterans, (6) Retrograde changes, (a) fatty degeneration of the intima, (6) calcareous infiltration with ossification, (c) amyloid disease, (7) Aneurysm; (a) causation and mode of production; injury to middle coat and increase of blood-pressure; (b) coats of artery in aneurysm; (c) thrombi; (d) condition of branches; (e) effects on the heart; and (f) on parts around; (g) terminations, by cure, by pressure effects, by rupture. (8) Special forms of aneurysm; (a) cirsoid aneurysm or aneurysm by anastomosis; (6) traumatic aneurysm; (c) dissecting aneurysm; (d) varicose aneurysm. (9) Syphilitic and tubercular affections of arteries.
THE blood-vessels are to be regarded as tubes of which the essential constituent is the intima. According to circumstances the intima becomes clothed with external and middle coats, and so we have arteries and veins. We have already seen that, in nearly all new-formations, blood-vessels are produced as well as the proper tissue, and it is first a tube composed of intima which is formed, or a capillary. This primary vessel is capable of enlargement and further complication in the way just indicated, so that a transformation of the primary capillaries into arteries and veins may take place. This formation of vessels and their further development according to the requirements of the tissues is an exceedingly common occurrence, and may be regarded as equivalent to that which occurs in the formation of the tissues during the period of development and growth of the body as a whole. A process of a similar nature is sometimes seen when the obstruction of an artery causes the current to be in great part diverted into other channels. We know that in this case the anastomosing vessels enlarge, small arteries becoming converted into large ones, and perhaps even capillaries into arteries. The vascular system is thus an •exceedingly plastic one, and possesses great powers of new-formation and development according to the needs of the tissues.