TEMPERATURE REGULATION IN HOMOIOTHERMS 63 



The Thermal Nerve Center. — Since many means are 

 brought to play in organisms for the maintenance of a 

 constant body temperature and especially since a variety 

 of nerves — ^vasomotor, muscular, secretory — are in- 

 volved, it is apparent that a coordinating center is re- 

 quired. Experimental evidence obtained by Barbour 

 (1921) and others indicates that such a center exists in 

 the corpus striatum. The gain or loss of heat by an 

 organism depends upon many interwoven factors such 

 as blood-content, colloids, water-content, various ions 

 and metabolites, and other physiological factors. These 

 probably maintain a fair degree of constancy in the poi- 

 kilotherms. But temperature regulation must depend 

 upon something more. It occurs in those species which 

 have a highly developed nervous system and only when 

 in those particular species the nervous system has 

 reached a certain stage of development in each individ- 

 ual. Therefore one concludes that in the evolution of 

 the temperature regulation a new function has been 

 added and that the nervous system has gained control 

 of those physiological processes which affect the gain 

 and loss of heat in the organism. Barbour (1921) clearly 

 demonstrated that the application of heat or cold to the 

 anterior end of the corpus striatum by means of a small 

 metal tube through which water of various temperatures 

 was circulated, caused marked changes in the body tem- 

 perature of the animal. "When cold objects were applied 

 to the nerve center, the rectal temperature rose and 

 shivering and vaso-constriction of the skin were also 

 observed. If objects having a temperature above that 

 of the body were applied, a fall in rectal temperature 

 and muscular relaxation and dilatation of the skin blood 

 vessels occurred. These results have been confirmed by 

 several later investigators. Barbour (1921) states that 



