ANIMAL LIFE IN GENERAL. 275 



The Organism of the Animal becomes sen- 

 sibly heated even to itself, in distinction from 

 the organism of the Plant, though the latter 

 too has its heat-scale. The normal tempera- 

 ture in man is usually placed at about 99 de- 

 grees (F.), from which any considerable devi- 

 ation is unhealthy. Other mammals vary 

 somewhat from this norm; it is highest in 

 certain birds, reaching 112 degrees (F.). The 

 heat of the animal body is simply a result of 

 chemical combustion ; from this point of view 

 our organism is but a chemical laboratory 

 maintained at a certain degree of heat neces- 

 sary to compose and decompose the various 

 constituents of life; too much or too little 

 heat would destroy the process. This ther- 

 mal equipoise is maintained within by the 

 higher animals both in the hotter tropics and 

 in the colder arctic regions. 



Biologists put stress upon what is called 

 a morphological distinction between the Plant 

 and the Animal : the former has a membrane 

 or coat of cellulose (with some exceptions), 

 the latter has no such coat (with some ex- 

 ceptions). Not much anchorage can be found 

 in that distinction. A common physiological 

 character is that both take food and trans- 

 form it through chemism into function partly 

 and into waste partly, the latter being thrown 

 off as excretion. This process is often called 



