Vasoconstriction in the human hand due to smoking was demonstrated in 1909.' Since then numerous studies have amply demonstrated that smoking causes cutaneous vasoconstriction. Intravenous injection of nicotine has been demonstrated to produce cutaneous vasoconstriction,2 and it is generally accepted that the important vasoactive ingredient in tobacco is nicotine.Cutaneous vasoconstriction following smoking or injection of nicotine has been determined by skin temperature r n e a~u r e m e n t ,~~~~~ observation of capillary beds,5 and plethysmograph.' An excellent brief summary of early work on cutaneous vasoconstriction caused by nicotine and smoking is given by Roth and associates.2The literature gives somewhat conflicting statements on the effect of nicotine on blood flow in skeletal muscle. I n the cat, intra-arterial injection produced both vasoconstriction and vasodilatation, very small doses causing vasodilatation, whereas larger doses resulted first in vasodilatation and then in vasoconstriction.6 In 1939 studies of the effect of smoking on the blood flow of the hand and forearm were used to provide a reasonable hypothesis that the smoking either produced no change in the flow in the muscles of the forearm, or an increase in the flow? This conclusion is based on the assumption that the blood flow in the skin of the forearm was similar to that in the hand, which is probably true but was not demonstrated.Further light was thrown on the subject in 1955 by Ruef and his associates* who, by use of the Hensel thermoelectric needle, were able to demonstrate by measurements in the muscle that smoking produced a moderate increase in the blood flow in human skeletal m u~c l e .~ Because of lack of quantitative data on the effect of smoking on skeletal muscle blood flow and no data on the effect of intravenously administered nicotine on blood flow in human skeletal muscle, it was felt that further studies were necessary, and that these studies should provide a clear distinction between changes in flow in muscle and in skin.
Methods and ProcedureForty-seven plethysmographic studies and 8 digital temperature studies were made on normal male subjects between the ages of 18 and 31 years. Initially both smokers and nonsmokers were used, but it was found that nonsmokers did not make satisfactory subjects because of frequent attacks of nausea,
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