INTELLIGENCE, POWER, 



Since we wished to make a further study of the influence 

 of climate upon the races of man, we made an expedition to 

 the Hawaiian Islands in 1939. In Dr. Nils P. Larsen, who has 

 himself made valuable contributions to the study of man, we 

 found a most cooperative collaborator. To Dr. Larsen we are 

 indebted for much valuable human material from Hawaii. 



In our dissections in the subarctic we were impressed by 

 the large brain, the large thyroid gland, and the large blood 

 volume found in the warm-blooded animals of the north 

 in contrast with the smaller brain, smaller thyroid gland, 

 and smaller blood volume found in comparable species in 

 the tropics. 



These observations suggested to me a study of the poten- 

 tial gradients of the brain and the blood under the influence 

 of the thyroid hormone. A long series of experiments con- 

 ducted by Otto Glasser, Ph.D., director of the Department 

 of Biophysics of the Cleveland Clinic Foundation, Dr. 

 Quiring, and me, showed that the thyroid hormone specifi- 

 cally increases the potential gradients, that is to say, the 

 thyroid hormone increases the rate of oxidation or metab- 

 olism and is a fundamental adaptation against cold. 



As a corollary, animals in the tropics, as an adaptation 

 against heatstroke, possess the smallest thyroid glands. 



The results of this research were reported by me, in 

 collaboration with Dr. Glasser and Dr. Quiring, before the 

 American Association for the Advancement of Science in 

 June, 1940. In 1941, when we found that we lacked that 

 unique animal the manatee and certain fish, a supple- 

 mentary expedition to Florida was made. 



The data from our various expeditions, as presented in 

 the following pages, show that the intelligence, power, and 

 personality of animals are indicated by the absolute and 

 relative size of the brain, the heart and blood volume, 

 the thyroid gland, and the adrenal-sympathetic system. 

 Whether in the sea, on the land, or in the air; whether in 

 the tropics or in the arctic; whether warm-blooded or cold- 



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