A failure of peripheral vascular tone in the upright position is a common cause of arterial hypotension, cerebral ischemia and syncope. The commonest form is vasodepressor syncope, with an active dilatation of resistance vessels, indicative of a crescendo, autonomic discharge in which cholinergic features predominate (perspiration, increased peristaltic activity, nausea, salivation and bradycardia). This type is the "common faint." Much less frequent and clinically much more grave is orthostatic hypotension due to sympathetic-nervous-system failure, in which the fundamental disturbance is a failure of reflex adrenergic cardiovascular activity to prevent hypotension from the normal pooling of blood below the right side . . .