452 TEXT-BOOK OF PHYSIOLOGY 



The regulation and maintenance of the mean temperature or thermotaxis 

 is, therefore, the result of an adjustment between heat-production and heat- 

 dissipation, both of which are variable factors, and is accomplished by a 

 complex, self-regulating mechanism consisting of muscle, vascular and secretor 

 elements coordinated by the nerve system. Given this mechanism and the 

 variations in the external temperature the metabolizing power of the living 

 material is caused to vary in one direction or another as the external tem- 

 perature rises and falls. 



