82 Milton Landowne 



available for study, a group of 78 were selected as suitable; 

 their ages ranged from 26 to 93, with a mean of 58. They 

 were chosen because they presented no disorder which we 

 thought would interfere with the test or its interpretation, 

 and because they had no symptoms to indicate the existence 

 of peripheral arterial disease. Eleven of these subjects were 

 considered to warrant functional classification according to 

 the American Heart Association standards as class 2 (mini- 

 mal impairment in reserve), and the remainder as class 1 (no 

 impairment). Each subject was studied twice. The skin 

 temperature was obtained at six sites by multiple point 

 automatic recording thermocouples. After equilibration for 

 90 minutes in a room constant at 22 • 7° C, reflex vasodilata- 

 tion was induced by specially designed radiant heating applied 

 to the trunk and abdomen. This method of eliciting a maximal 

 vasodilatation in fingers and toes was selected as convenient, 

 efficient, and well tolerated. Subject acceptance of procedure 

 is, of course, a prime requisite of experimental design. 



From a study such as this, we have come to these conclu- 

 sions: under standard conditions, these 78 subjects, without 

 evident peripheral vascular disorder, showed a uniform tem- 

 perature of the fingers and a slight but statistically significant 

 age wise increase in the temperature of the toes. The observa- 

 tion that older subjects have warmer toes, under these condi- 

 tions, does not support the idea of any decrease in resting 

 skin flow with age. Since blood flow is relatively low under 

 these conditions, and skin temperature is only an indirect 

 index of flow, it cannot be concluded that resting flow to the 

 toes increases with age. In some older subjects, toe tempera- 

 ture exceeded finger temperature, showing a reversal of the 

 finger-toe gradient which is considered to characterize the 

 relative vaso-motor participation of the upper and lower 

 extremities in heat regulation. These are evidences for a 

 change with age in the differential heat-regulating activity of 

 the upper and lower extremities. There may, therefore, be a 

 greater relative heat loss by radiation in the toes of older 

 individuals at rest in a cool environment, due either to a greater 



