PROCEEDINGS OF THE COTTESWOLD CLUB 63 



taking place between the animal body and the surrounding 

 medium, the temperature of the former must be in such 

 animals largely dependent on the latter rising and Jailing 

 with it. Hence most of the lower animals are poikiloth- 

 . ermic, or, as they not so accurately, but more commonly, 

 designated, cold-blooded. The higher animals on the 

 contrary in which, on account of their highly-developed 

 resjjiratory organs and energetic metabolism, the thermo- 

 genic activity is great, and which are protected from a 

 rapid loss of heat by radiation by the size of their bodies 

 and bv the possession of a covering of hairs or feathers, 

 or some artificial covering, possess the power of main- 

 taining a somewhat constant temperature, which is largely 

 independent of the rising or falling of the temperature of 

 the surrounding medium. Such animals are called 

 homothcrmic, or warm-blooded. Since they require a 

 high internal temperature, varying only within compara- 

 tively small limits, as a necessary condition for the normal 

 course of the vital processes, or one may say for the 

 maintenance of life itself, they must possess within them- 

 selves a series of what may be termed regulators, whose 

 function it is to keep the body-temperature within its 

 projjcr limits with relation to the temperature of the 

 surrounding medium. This may be effected either by 

 diminishing the production of internal heat (diminishing 

 the metabolism) or by increasing the loss of heat from 

 the surface of the body (by radiation, evaporation of 

 secretions, or cooling in water), w^hen the temperature of 

 the surrounding medium is high ; and on the contrary, 

 when it is low, by increasing the production of internal 

 heat (increasing the metabolic energy) by a more plentiful 

 food supply, more vigorous movements and so on ; or 

 also, by diminishing the loss of heat by the use of more 

 effectually-protective coverings. When the conditions 

 necessary for the action of what I have called these 

 " regulators " are absent, as in the case of want of food, 

 or, in the case of small and unprotected bodies, we find 



