These conditions having been somewhat fully discussed in previous pages, it remains here to refer to the more local changes.

Thrombosis occurs as a secondary result of disease of the walls of arteries, chiefly in cases of atheroma and aneurysm. In the former it is often the cause of the final closure of the vessel. There is also thrombosis as a result of ligature of arteries. Acute inflammations in arteries also induce thrombosis; this is especially the case in septic inflammations. There may be in this way a condition similar to the more frequent septic thrombosis in veins (thrombo-phlebitis).

Embolism is very frequent in arteries. If the embolus be a simple one, such as a piece of thrombus, the portion of artery affected will undergo a process of chronic inflammation and the plug will become organized in the manner about to be described. A septic embolus, on the other hand, will become the centre of a suppurative inflammation. We have also embolism from the penetration of tumours and parasites.