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BOOKS AND CURRENT LITERATURE 



pressed in terms of very general characteristics, and their statement 

 becomes more specific as knowledge advances. Thus, many writers have 

 pointed out that the adaptation to seeing which is manifest in the verti- 

 brate eye is a function primarily of the manner in which this organ devel- 

 oped, this manner having been dependent upon the development of the 

 various component tissues and cells. The components have developed 

 as they have because of final causes, a primal impetus (Bergson) or 

 entelechies (Driesch), and so on. To one who appreciates the progress 

 already made by natural science toward a knowledge of specific prop- 

 erties of objects such explanantions are unsatisfactory, not because 

 they are not true but because they are not true enough; they do not 

 express enough of the truth. Explanations must always lack finality, 

 from the very nature of the universe, but they must not (and hypothet- 

 ical explananations should not) fail to present their propositions in the 

 most fundamental terms that may be possible at the time. Now, while 

 the characteristics of living things are in many cases not yet referable to 

 the fundamental variables of physical science (time, space, matter and 

 energy) , the characteristics of the environment of living things are thus 

 referable, and it is this sort of reference with which the book before us 

 deals. Professor Henderson has set forth a very complete study of the 

 most fundamental physical and chemical properties of matter and the 

 characteristics of energy, as these condition the attributes of the general 

 environment which render the latter adapted to plants and animals. 



Since it is only possible to study the fitness of the environment with 

 reference to certain characteristics of the things environed, and since such 

 characteristics of the things environed, must be as fundamental as pos- 

 sible, still being applicable to all living things, the author is led at the 

 outset to erect three postulates as expressing the primary requisites for 

 the existence of organisms. First, the organism must be physically and 

 chemically complex, more so than other objects in nature; second, the 

 physical and chemical conditions within the organism must be compa- 

 ratively stable, they must not vary beyond defined limits; and third, 

 there must ever be an interchange of material and energy between the 

 organism and its surroundings. The problem thus inquires: through 

 what properties of matter and energy is it possible for objects to exist 

 that are characterized by a high degree of complexity, regulations of con- 

 ditions, and metabolism? The main features of the material environment 

 are taken for the present discussion, as water, carbon dioxide and the 

 three chemical elements derived from the decomposition of these com- 

 pounds. The author proceeds to set forth a host of physical and chem- 



