4 ANIMAL STUDIES 



matter, or the changing of organic matter of one kind, as 

 plant matter, into another kind, as animal matter ; motion, 

 the power of spontaneous movement in response to stimuli ; 

 sensation, the power of being sensible of external stimuli ; 

 reproduction, the power of producing new beings like them- 

 selves ; and adaptation, the power of responding to external 

 conditions in a way useful to the organism. Through adap- 

 tation organisms continue to exist despite the changing of 

 conditions. If the conditions surrounding an inorganic 

 body change, even gradually, the inorganic body does not 

 change to adapt itself to these conditions, but resists them 

 until no longer able to do so, when it loses its identity. 



4. Primary conditions of animal life. Certain primary 

 conditions are necessary for the existence of all animals. 

 We know that fishes can not live very long out of water, 

 and that birds can not live in water. These, however, are 

 special conditions which depend on the special structure 

 and habits of these two particular kinds of backboned ani- 

 mals. But the necessity of a constant and sufficient sup- 

 ply of air is a necessity common to both ; it is one of the 

 primary conditions of their life. All animals must have 

 air. Similarly both fishes and birds, and all other animals 

 as well, must have food. This is another one of the pri- 

 mary conditions of animal life. That backboned animals 

 must find somehow a supply of salts or compounds of lime 

 to form into bones is a special condition peculiar to these 

 animals. 



5. Food. All the higher plants, those that are green 

 (chlorophyll-bearing), can make their living substance out 

 of inorganic matter alone that is, use inorganic substances 

 as food. But animals can not do this. They must have 

 already formed organic matter for food. This organic mat- 

 ter may be the living or dead tissues of plants, or the living 

 or dead tissues of animals. For the life of animals it is 

 necessary that other organisms live, or have lived. It is 

 this need which primarily distinguishes an animal from a 



