FITNESS 33 



it has also acquired an environment, a milieu 

 interieur for its cells, — like the blood and 

 lymph, — which serves the same purpose as 

 stability of the external environment, and ex- 

 ercises the further function of supplying food. 



It is through this structure, in the process 

 of metabolism, that matter and energy flow. 

 Entering in various forms and quantities, 

 they are temporarily shaped exactly to the 

 form and condition of the organism; they 

 conform to the characteristics of the king- 

 dom, class, order, family, genus, species, and 

 variety to which it belongs, and they assume 

 even the characteristics of the individual 

 itself. 1 Then they depart through the va- 

 rious channels of excretion. 



When these ideas are reduced to their very 

 simplest forms, it appears that life must be 

 highly complex in structure and function; 

 that the conditions of the environment must 

 be regulated, and that there must be very exact 

 regulation of conditions, both structural and 

 functional within the organism, and finally, 

 that, while life is active, there must be ex- 

 change of both matter and energy with the 

 environment. Complexity, regulation, and 

 food are essential to life as we know it, and 



1 Science is, of course, still at a loss for an adequate gen- 

 eral explanation of such processes. 



