CHAPTER X. 



ANIMAL HEAT. 



INORGANIC bodies have a constant tendency, either by losing or 

 gaming heat, to adapt themselves to the temperature of surrounding 

 media or objects. They may be artificially cooled or artificially 

 heated to all possible degrees. 



Living plants and animals also receive and give off heat physic- 

 ally; but, in addition, they possess a common power of resisting 

 external temperatures. With the plants this power is very feeble in 

 degree ; with animals it is more marked. Among the higher animals, 

 especially, is there an inherent power to maintain a temperature that 

 differs from that of the surrounding media. Since living animals, 

 like dead ones and inorganic bodies, exhibit the same physical phe- 

 nomena of absorption, conduction, and radiation of heat, they un- 

 dergo constant changes; these are usually in the direction of loss of 

 heat. Hence there must exist within them a power of constant 

 renewal or production of heat to take the place of that lost. This 

 function of producing heat is universal with the warm-blooded ani- 

 mals, and all of the processes of life are influenced by it. Certainly 

 the higher animals have within their bodies not only some means to 

 produce heat, but some mechanism whereby the production and loss 

 are regulated. Thus, though the temperature of the surrounding 

 atmosphere be very high, as in midsummer, or very low, as in mid- 

 winter, yet the standard temperature of the animal's body remains 

 uniform and constant. The energy necessary to accomplish this is 

 known as animal heat. 



Physical Heat. Heat is a form of energy exhibited by matter. 

 We cannot create or destroy either. 



Energy is the power to do work. Any agent that is capable of 

 doing work is said to possess this property. The quantity of energy 

 that it possesses is measured by the amount of work it can do. When 

 a body is hot it possesses a store of energy which may be exhibited by 

 the heated matter. 



Energy is known in two forms: 1. The energy possessed by a 

 body in consequence of its velocity is known as energy of motion, or 

 Tcineiic energy. The body in motion which has this kinetic energy 

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