CONNECTION OF RESPIKAT10N AND HEAT. 177 



which the respiratory apparatus works, for it is through its agency that air 

 is introduced. Extensive observation accordingly establishes a close cor- 

 respondence in each animal tribe between the quantity of heat produced and 

 the capability of respiratory apparatus. The lower tribes breathe sfbw- 

 ly and are cold. Earthworms are only a degree or two warmer than the 

 ground ; and even among vertebrates, fishes are only two or three degrees 

 warmer than the water, a lowness of temperature in a great ^measure de- 

 pending on the high cooling agencies which that liquid ex- Connection of 

 erts, its specific heat, and the facility with which currents are respiration and 

 established in it. However, even in these cases the produc- L 

 tion of heat depends on the power of the respiratory engine. The bonito 

 can keep its heat 20 above that of the sea, and the narwhal maintains 

 a steady temperature at 96. 



The organic operations involved in nutrition, and also the retrograde 

 changes of decay, can only go on at their accustomed rates so invariability 

 long as standard limits of temperature are observed. The of organic ac- 



, . m-f T T " OT implies a 



proper progress of the actions of life implies a corresponding definite tem- 

 adjustment of heat, and this irrespective of the mere size of P erature - 

 the animal. Even those that are microscopic must come under this rule. 

 When the temperature of a liquid containing infusorials is caused to de- 

 scend to the freezing point gradually, the last portions which solidify are 

 those which surround each of these little forms ; a drop is kept liquid by 

 the heat they disengage. In the same individual, the absolute tempera- 

 ture will depend on its respiratory condition ; thus insects, in passing 

 through each of their stages of metamorphosis, present a definite condi- 

 tion as to their heat: the larva of the bee may be only two degrees above 

 the air, while the perfect insect is 10. Whatever accelerates the in- 

 troduction and expulsion of the air, increases the warmth; Variations of 

 so a bee shaken in a bottle, and kept in a state of constant ^0^0* d 

 muscular exertion, will raise the temperature contained there- tion. 

 in far higher than if he remains inactive. Among insects, those having 

 the largest organs of respiration have always the highest temperature ; 

 and, since muscular motion implies destruction of muscular tissue by ox- 

 idation, and therefore development of heat, we should expect to find, as 

 is actually the case, that animals possessing the highest powers of loco- 

 motion will possess also the highest temperature. Of all, therefore, birds, 

 the endurance and energy of whose powers of flight result from the per- 

 fection of their respiratory mechanism, have the highest temperature. It 

 is about 110. Yet even here there are differences : the sluggish barn- 

 door fowl has not the heat of the energetic swallow. 



The standard temperature of man is usually stated to be 98, but from 

 this mean it ranges within certain limits upward and down. Temperature 

 Much depends on the state of the health; of course, every thing of man - 



M 



