In order to obtain an accurate picture of the state of the peripheral circulation it is necessary to know the blood flow and the vasomotor reactions in as many parts of the body as possible. An investigation of the blood flow and the vasomotor reactions of parts of the upper and the lower extremities is of particular significance, not only because of the wide variations in the proportion of muscle to skin in the different parts of the extremities, but also because of the presence in the skin of the hands and feet of numerous arteriovenous anastomoses which have not been demonstrated in other parts of the body (1). In order, therefore, to secure a more complete understanding of the peripheral circulation, the blood flow and the vasomotor reactions in the hand, forearm, foot, and calf at rest were studied by plethysmographic methods. In-addition, the changes in the blood flow following exercise and arterial occlusion and the effect of epinephrine and of pitressin on the blood flow were observed in these four parts of the body. METHODThe subjects selected for this study had normal cardiovascular systems. The hand was studied in the plethysmograph described by Freeman (2) and the foot in that described by Stead and Kunkel (3). The plethysmograph of Lewis and Grant (4) was used for the forearm and a similar one of larger size was constructed for the calf. In each case the rubber cuffs closing the instruments were attached to the skin by rubber cement in such a manner as to cause no elevation of the venous pressure; they were prevented from bulging outward by suitable firm, fitted diaphragms. The instruments were connected by pressure tubing to Brodie bellows of 14 cc. capacity which recorded the changes in volume on a smoked drum. In order to maintain the water within the forearm and calf plethysmographs at a constant temperature, the instruments were surrounded by large 'The expense of this investigation has been met in part by a grant from the Proctor Fund of Harvard University for the Study of Chronic Disease. water baths; the hand or foot distal to them was exposed to the air. In experiments in which the blood flow and vasomotor reactions of the hand and foot were studied, the water surrounding these organs was constantly circulated by motor driven propellers, but that surrounding the arm and the calf was not mechanically stirred. The water baths were maintained at a constant temperature for at least 30 minutes before blood flow determinations were made. All observations were made with the subjects horizontal and the parts to be tested resting comfortably in the instruments at heart level. In order to measure simultaneously blood flows and vasomotor reactions in various organs, two or three plethysmographs were usually applied, though in no case was more than one instrument applied to the same extremity.These plethysmographs could be used for the determination of the blood flow to the enclosed portion of the extremity, since the initial rate of increase in volume produced by applying a collecting pressure just pr...

Reviewing the literature, a male predominance, low rate of SAH, high percentage of complex aneurysms and of aneurysms located in the posterior circulation are characteristic features of aneurysms in childhood. Once a cerebral aneurysm is diagnosed in the younger age group, definite therapy should be performed soon as the outcome is expected to be more favourable than in adulthood.

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The nature of the arteriolar resistance and its distribution in the body remain the fundamental problem in the study of arterial hypertension in man. Since the cardiac output is normal in this state (1), the " average arteriolar resistance " at rest must be increased. The extent to which the peripheral resistance is increased in various tissues can be determined by comparing the blood flow in the different tissues in both normal and hypertensive subjects under similar conditions. If in arterial hypertension the peripheral resistance in any one part is not increased, the blood flow in that part will be greater than in normal subjects.Since the cardiac output at rest is normal in arterial hypertension, the "average tissue blood flow " must also be normal. This has been confirmed by the demonstration that in hypertensive subjects the blood flow is normal in the hand and forearm (2, 3). While it is of interest to gather further information on the " resting " blood flow in other organs in normal and hypertensive subjects, it is of particular importance to ascertain whether the increased peripheral resistance in arterial hypertension can be lowered to a normal level in any one organ by potent vasodilating stimuli. If the increased peripheral resistance which exists at rest in arterial hypertension can be lowered to normal in any one organ, as manifested by a faster blood flow than is present in that organ in normal subjects under similar conditions, then the increased peripheral resistance at rest is the result of functional vasoconstriction, and is not the result of permanent, irreversible structural changes in the vessels. If the increased peripheral resistance present in arterial hypertension, however, cannot be reduced to normal by powerful vasodilating stimuli, as indicated by the finding of the same blood flow in the tissues of both normal and hypertensive subjects when the vessels are maximally dilated, then there are at least two obvious explanations: The chemical or other factors, which cause the vasoconstriction and the increased peripheral resistance, remain active in the presence of the various physiological stimuli applied and prevent the vessels from dilating as widely as normally; or the increased peripheral resistance is the result of permanent structural changes and, therefore, the vessels cannot dilate as widely as normally.Other investigators have shown that the increased peripheral resistance, which is present in the usual types of clinical arterial hypertension, is not reflex or neurogenic in origin. Prinzmetal and Wilson (2) demonstrated that on eliminating the vasoconstrictor influences by heating the body, or by novocainization of the sympathetic ganglia, the blood flow in the forearm in subjects with arterial hypertension increased as much as, but no more than, in normal subjects. They concluded, therefore, that, as the peripheral resistance remained increased in arterial hypertension after the removal of all vasconstrictor impulses, it could not be neurogenic in origin. Recent work, howeve...