B. =Local Causes.=--These are largely connected with _ischemia_. _Gangrene from edema_--itself the result of passive hyperemia and exudation--is not infrequent, the most common expression of this condition being seen perhaps in the external genitals of the male. _Embolism_ due to valvular heart disease, _thrombosis_ due usually to a preceding phlebitis, but possibly to marasmic origin, especially met with after confinement, with disturbance in the uterine sinuses, shutting off the circulation by endarteritis, which thus assumes the form _obliterans_, are some of the local causes which concern the bloodvessels alone. In fact, the majority of cases of spontaneous gangrene are probably due to changes in the vessels, endarteritis being the cause of a condition known as atheroma of vessels, in which fungoid outgrowths, or, rather, ingrowths into the vessel lumen, are common. Any one of these, if detached, may serve as an embolus. The degenerative excavations in the thickened walls of the bloodvessels, which discharge more or less cholesterin and other debris, and which have been known as _atheromatous abscesses_ (misnomer), are frequently the precursors of the disease under consideration. As the result of these changes alone, without reference to formation of emboli, vessels may become completely occluded, especially when slightly injured.[2] [2] Intermittent claudication, when recognized, may be regarded as a precursor of that arteriosclerosis which may proceed to gangrene. The term implies temporary anemia of one or more of the extremities, with numbness, burning, or prickling sensations in the skin, occasional cramps in the muscles, with loss of power, tenderness of the nerve trunks, weakening or loss of pulse in the affected part. When these symptoms occur in the feet they are not infrequently followed by terminal gangrene or other evidences of angioneurotic necrosis, including even those forms known as erythromelalgia and Raynaud’s disease. Its treatment, of course, is relaxation of vasomotor spasm, best accomplished by the use of the nitrites, among which nitroglycerin is perhaps most valuable.