80 Milton Landowne 



particularly by the addition of relevant and critical evidences 

 from several different points of view. 



As an illustration of a quasi-specific study, I might outline 

 the approach and results of some observations of skin tempera- 

 ture which we have made (Landowne, Silver and Silverstone, 

 1954). The physiological literature refers to statements that 

 skin temperature is higher during the more active and robust 

 years and decreases with advancing age, but it does not yield 

 critical data in this regard. Because of the reduction in basal 

 metabolism with age, the older subject loses less heat to his 

 environment. It is then to be expected that a reduction occurs 

 in the heat transferred by the blood flow to the skin. The 

 popular concept and interpretation of subjectively cooler 

 extremities in some older individuals is that of a reduced 

 resting peripheral circulation. Agewise changes in cutaneous 

 circulation might alter the efficiency of body temperature 

 regulation and might also underlie the age changes in structure 

 and functions of the skin. In moderately cool, still air at 

 constant temperature, heat losses by convection and evapora- 

 tion are minimized and the tctal heat loss, which occurs 

 chiefly by radiation, is proportional to the skin temperature. 

 In this manner, the skin temperature can provide an index of 

 the cutaneous circulation and of the heat loss under resting 

 conditions. In addition, under conditions of induced vasodila- 

 tation, the skin temperature can yield information as to the 

 functional integrity and reserve of major arteries, as well as of 

 the cutaneous blood supply. The analysis of the temperature 

 response of the skin to heating of the trunk is taken to be an 

 indication of the maximal blood flow to the skin. The maximal 

 cutaneous blood flow is, in turn, considered to reflect the 

 minimal vascular resistance of the skin circulation, and by 

 presumption, on the average, of the circulation in the entire 

 limb. The commonly encountered cause of fixed increase in 

 vascular resistance (except in hypertensive subjects) is 

 arteriosclerosis of the major arteries. The portion of the total 

 regional or planetary population available for investigation 

 (Fig. 4) may be considered to include an undetermined and 



