Mast, L. J. Henderson on "The Fitness of the Environment". 435 



The environment is recognised as consisting of numerous fac- 

 tors. The most important of these the author holds, are C0 2 and 

 H 2 O, and his conclusions regarding the fitness of the environment 

 are based on a treatment of these factors. Thus the author main- 

 tains (p. 63) that "Living things permit themselves to be simplified 

 into mechanisms which are complex, regulated, and provided with 

 a metabolism, the environment, by a series of eliminations, is 

 reduced to water and carbonic acid." But he says, on the same 

 page, "These are simplifications counseled solely by expediency. 

 Neither logical process is necessary; each involves a disregard for 

 many circumstances which might be of weight in the present 

 inquiry." 



The problem which Henderson has set for solution consists 

 not only of the question as to how fit the environment is for the 

 continuous existence of a complex, durable, automatically regulated 

 system (life), but also of the question as to how it happens that 

 it is fit at all. He says (p. 66), "Water is indeed a wonderful sub- 

 stance which fills its place in nature most satisfactorily, but would 

 not another substance do as well? Is not ammonia, for example, 

 a possible substitute?" and (p. 67), "It will be necessary to find 

 out whether these substances are not only fit but fittest" ; and 

 again (p. 37), To what extent do the characteristics of matter and 

 energy and the cosmic processes favor the existence of mechanisms 

 which must be complex, highly regulated, and provided with suitable 

 matter and energy as food? If it shall appear that the fitness of 

 the environment to fulfill these demands of life is great, we may 

 then ask whether it is so great that we cannot reasonably assume 

 it to be accidental, and finally we may inquire what manner of 

 law is capable of explaining such fitness of the very nature of 

 things." 



The only point in this section of the book regarding which 

 there is likely to be much controversy concerns the idea of necessity 

 introduced in connection with the definition of life. Organisms 

 have been observed to be very complex and relatively durable; 

 and they have been seen to possess, within certain limits, the power 

 of regulation (adjustment). But is this adequate reason for assum- 

 ing that they must necessarily be as they are? Are they not as 

 they are simply owing to the action of their surroundings, and 

 could not living beings, radically different, exist if the environment 

 were quite fifferent? These questions will come up again later. 



The second part of the book covers 200 pages devoted to a 

 detailed study of the properties (chemical and physical) of H 2 and 

 C0 2 , their elements, and various compounds derived from them 

 with reference to their fitness for the use of living beings. It is 

 concluded from this study that these compounds, forming the very 



