68 HOMOIOTHERMISM 



ing as a result of the direct increase of metabolism by 

 adrenin and that this compensates for heat loss. 



Some observations reported by early workers indi- 

 cate that the pituitary decreases in size during hiberna- 

 tion but enlarges again and becomes more vascular when 

 an animal awakens. Easmussen (1921) however believes 

 that changes in the pituitary are not a cause of hiberna- 

 tion. He bases his conclusion on experiments with a 

 large number of woodchucks. The pituitary hormone 

 exerts a marked influence on the water balance of 

 the body (Eowntree, 1922) and therefore would aifect 

 the regulation of bodily temperature. Falta (1923) 

 states that hypophysial dystrophy is always accompanied 

 by abnormally low body temperatures. The hypophysis 

 apparently promotes temperature regulation on account 

 of its influence on the nervous system. 



One may conclude from the observations made in the 

 study of endocrinology that hormones doubtless play an 

 important role in the control and maintenance of the body 

 temperature. Since little is known of the reciprocal ac- 

 tion of hormones, the exact part they play is still some- 

 what hypothetical. Future investigation will likely add 

 much to knowledge of their mode of action and this is a 

 promising field for study. 



