TEiMPERATURE REGULATION IN HOMOIOTHERMS 67 



perature regulation of homoiotherms. The thyroid has 

 marked effects upon the oxidative processes and also 

 influences heat production. Mansfield and Pap (1920) 

 emphasized the relationship between heat regulation and 

 the control of the thyroids over oxidation. It has been 

 observed also from clinical practice that thyroidectom- 

 ized animals regulate their temperatures with difficulty. 

 The more pronounced disturbances of heat regulation 

 seem to occur most commonly and most strikingly in con- 

 nection with diseases of the thyroid gland. In myxedema 

 the body temperature often drops far below normal. In 

 exophthalmic goiter, hyperthermia is commonly reported. 

 Structural variations in the thyroid which vary accord- 

 ing to environmental temperatures are described by Bar- 

 bour (1921). 



The influence of insulin upon body temperature has 

 been observed by Cassidy, Dworkin, and Finney (1926). 

 These investigators studied the relation of sugar me- 

 tabolism to hibernation in mammals and found that if 

 insulin was injected and the blood sugar thus decreased, 

 the shivering reflexes were absent when the animal was 

 subjected to cold. 



Erection of hairs, ruffling of feathers, constriction of 

 peripheral blood vessels, and increase of blood sugar 

 have been mentioned as responses of homoiotherms to 

 cold temperatures. The investigations of Cannon, 

 Querido, Britton, and Bright (1927) indicate that adrena- 

 lin brings about such responses and furnishes a means 

 for protecting the organism against cooling. They found 

 that by producing a heat debt in animals an increased 

 activity of the medullary portion of the adrenal gland 

 was induced and that this led to an extra output of 

 adrenin, which in turn hastened combustion. They also 

 believe that heat is produced in the body without shiver- 



