ANIMAL HEAT. 



as well. The alimentary canal during digestion and also the liver are 

 very marked sources. In fact, the blood in the hepatic veins is the 

 warmest part of the body. The function of the muscles,, tendons, 

 ligaments, and bones is not a very slight source of warmth. 



It must be borne in mind by the student that the processes of 

 oxidation are concerned not only in the combustion of the digested 

 foodstuffs, but also of the cells of the body. It is the oxidation of 

 their protoplasm that evolves warmth. 



Warm-blooded and Cold-blooded Animals. Depending upon the 

 relationship of the temperature of the animal's body and that of 

 the enveloping media there are two great classes: homothermal and 

 poikilothermal. 



The homothermal, or warm-blooded, animals include the higher 

 orders of the animal kingdom, in whom the temperature remains 

 fairly constant despite variations in temperature of the enveloping 

 media. The temperature of this class of animals is high, but uni- 

 form. Should homothermal animals remain for a considerable 

 length of time in a cold medium, their heat-producing organs become 

 more active in order to compensate for that lost rapidly by radiation. 

 When they remain in very warm media, heat-production is dimin- 

 ished. 



Poikilothermal, or cold-blooded, animals constitute that class of 

 lower animals whose temperature bears a very intimate relationship 

 and is dependent upon that of the enveloping media. Their tem- 

 perature is thus subject to very considerable variations, although it 

 is always slightly above that of its surroundings. When the tempera- 

 ture of the surrounding medium is raised, the amount of heat pro- 

 duced within poikilothermal animals is increased. Inversely, when 

 the enveloping temperature falls, the heat-production within the ani- 

 mal is diminished. This class includes reptiles, amphibians, fish, and 

 most invertebrates. 



However, the line of demarkation between the two classes of 

 animals is not a very clear and decisive one. For there are some 

 animals, as the bat and dormouse, which seem to be intermediary. 

 In summertime they possess a high temperature that is independent 

 of their surroundings; in winter they become dormant and hiber- 

 nate. While in this latter condition their temperature varies with 

 that of the enveloping medium. 



Temperature of Man. Although the blood in circulation tends 

 to distribute the heat of the body uniformly, yet there are found 

 slight variations in different regions. These regions are principally 





