AND PE RSONALITY 



These principles interpret the evolution of the warm- 

 blooded animals. 



Through van't HofPs law one can understand why there 

 is a critical temperature, or ceiling, of about io8.5F., 

 beyond which detonation or heatstroke occurs. This uni- 

 versal menace of heatstroke not only limits the size of the 

 brain, the thyroid gland, the adrenal glands, the heart and 

 blood volume in man and animals in the tropics but, since 

 the speed of chemical activity of the body is increased 10 

 per cent with each degree of rise of temperature, the higher 

 the temperature of an animal the greater its speed and 

 power. In consequence, natural selection has endowed ani- 

 mals and man with a larger brain, a larger thyroid gland, a 

 larger heart and blood volume in the arctic than in the 

 tropics. 



In the foregoing argument, from an energy point of view, 

 we have differentiated man from the lower animals, and 

 civilized man from native man. Let us now consider our 

 tenth biological principle, that the thinking brain of man 

 has a unique survival value, which illuminates the diseases 

 peculiar to civilized man in the temperate zone. 



Among the Eskimos in the far north, the thinking brain 

 has much less survival value than in the temperate zone. 

 In the arctic there are no agriculture and no manufacturing. 

 The Eskimo lives on raw flesh. Intelligence can serve him 

 only to the extent of making him more crafty than the 

 whale, the seal, the walrus, or the bird and enabling him to 

 clothe himself with skins and to build an igloo, a sledge, 

 and a kayak. 



The thinking brain has less survival value, also, in the 

 tropics than in the temperate zone. In the tropics the 

 native needs only to fish and to gather fruit, berries, bird's 

 eggs, and nuts. Agriculture is rudimentary, and the produc- 

 tion of small grains cannot be successfully carried on be- 

 cause of the intense heat. 



But even in the arctic and the tropics the survival value 



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