194 THE ACTION OF THE LIVING CELL 



dietary considerations. Nevertheless such attempts 

 have frequently met with lack of success, even in the 

 hands of experienced husbandrymen. It is of inter- 

 est, therefore, to inquire into the relationship betw^een 

 such factors as those mentioned above and the various 

 aspects of the cytost problem that have been con- 

 sidered in the preceding pages. 



First consider the question of diet. As is well 

 known, a given diet may be entirely adequate for an 

 animal when regarded solely from the standpoint of 

 energetics, and yet be inadequate in so far as it is 

 lacking in essential components which the animal is 

 incapable of synthesizing from other components of 

 its food. It is evident, then, that before attempting 

 to breed a given species on a large scale one should 

 carefully study the dietary requirements of the ani- 

 mals at hand. Information as to the types and quan- 

 tities of food demanded by the ordinary domesticated 

 animals is usually obtainable, although it must be ad- 

 mitted that in most instances such needs have been 

 determined as a result of empirical experience rather 

 than by carefully planned investigations such as those 

 Osborne and Mendel have made upon the rat. 



The accumulated experience of years has taught 

 husbandrymen that aside from an adequate diet, cap- 

 tive wild animals and domestic animals must be pro- 

 vided with adequate facilities for exercise, and kept 

 under conditions which preclude crowding. The 

 necessity of considering such factors in the care of 

 animals is easily understood in the light of the vari- 

 ous experiments conducted with cytost, and we may 

 profitably consider them from the standpoint of the 

 cytost theory. 



