HUMAN RACIAL PESPONSES 



allowed greater cooling of the core and shell, their thermal conduc- 

 tance was significantly less, and their average skin temperatures 

 were considerably lower. The low tissue conductance in the tropical 

 natives resulted in skin temperatures which were intermediate be- 

 tween those of the Europeans and Pitjandjaras. The rectal tempera- 

 tures were the same in the tropical natives and European controls. 

 It was concluded thatthe Australian aboriginals had an inborn ability 

 to tolerate greater body cooling without recourse to metabolic com- 

 pensation and that this tolerance could be increased by prolonged 

 exposure to cold. 



Australian summary. Australian aborigines lying naked on the 

 ground find low skin and rectal temperatures compatible with sleep 

 (Hicks et al., 1934 and Morrison, 1957). Central Australian abori- 

 gines, when contrasted with European controls in a moderately cold 

 sleeping environment, do not elevate their heat production despite 

 low skin and rectal temperatures either in winter (Scholander et al., 

 1958) or summer (Hammel et al., 1959). 



The American Negroes 



American Negroes were transported as slaves from the old 

 empires of Ghana, Melle, and Songhay in West Africa. The Negro- 

 American population is by no means pure, and it is considered a 

 race in the process of formation by several recent authors (Goon 

 et al., 1950). 



Responses to whole body cooling . Rennie et al. (1957) exposed 

 eight male Caucasian soldiers and eight male American Negro 

 soldiers for 90 minutes to -12 C in summer and winter. Subjects 

 were clothed except for hands and fingers. The Caucasians had a 

 higher heat production, and the increase in metabolism was delayed 

 in the Negroes. After 70 minutes the Negro rectal temperature was 

 significantly lower. Although the average skin temperature was the 

 same, the Negro hands and feet were colder. 



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