456 BIOLOGY. [Book vii. 



Heat, then, is produced in every organised body, in a feeble 

 quantity in vegetals and the lower animals, with more energy 

 in the higher organisms. It is produced in all the organs, 

 tissues, and anatomical elements ; but very unequally, according 

 to the conditions of time and place. It is the general circulation 

 which levels, iu a certain degree, the various local temperatures, 

 which distributes with a certain equality the created heat, which, 

 moreover, thanks to the vaso-motory nerves, regulates the ex- 

 penditiu-e and temperature of each organ. 



The quantity of heat thus produced is variously employed. 

 One part is dissipated and lost by conduotibility, radiation, 

 evaporation; another part serves to maintain the organic 

 temperature at a proper degree ; finally a last part is directly 

 transformed into mechanical labour, as happens, in steam 

 engines, with the heat developed by the combustion of carbon, 

 for, in spite of their complexity, their mobility, the biological 

 phenomena, like physical phenomena, all are included in the 

 law of the correlation and transformation of forces, as we shall 

 show in the following chapter. 



