340 



SCIENCE 



[N. S. Vol. XXXVIII. No. 975 



elementary properties of the elements and com- 

 pounds entering into the formation of proto- 

 plasm. Considered in this light alone, the 

 book is remarkable for the breadth and in- 

 genuity of its treatment and for calling atten- 

 tion to many facts and principles the impor- 

 tance of which is often overlooked. To many 

 readers this will constitute its chief interest. 

 This, however, is not exactly the reviewer's 

 opinion. The question of the final signifi- 

 cance of biological adaptations is raised in a 

 novel and interesting, form, and some further 

 discussion of this question seems called for 

 here. What, after all, is meant by this con- 

 ception of adaptation? Considered from the 

 most general point of view, it seems best to 

 regard adaptation as essentially an instance of 

 equilibrium, though of a complex kind.^ 

 Equilibrium is a conception of physical sci- 

 ence, and as such susceptible of exact defini- 

 tion ; to regard adaptation in this light implies 

 that the problems which it presents are essen- 

 tially physiological in their nature, and hence 

 relegates the teleological point of view to the 

 background. This is always advantageous for 

 physical science, however it may be for prac- 

 tical life or philosophy. To many, the state- 

 ment that adaptation is an equilibrium may 

 seem either metaphorical or a truism; to the 

 physiologist it embodies a definite conception 

 of the organism as a physico-chemical system 

 which maintains its existence by a continued 

 succession of automatic compensations. What 

 we observe is that the adult organism pre- 

 serves its characteristics intact, for a greater 

 or less period of time, in spite of continual 

 loss of material and energy to the environ- 

 ment. Now, the processes by which this loss 

 is balanced by a corresponding intake, thus 

 enabling the life-processes to continue, are 

 just those which we characterize as " adaptive." 

 The structural and functional adjustments 

 necessary to maintain this balance are often 

 delicate and complex in the higher organisms ; 

 they involve the existence of special mechan- 



' Adaptation is treated from this point of view 

 in Paul Jensen 's ' ' Organische Zweokmiissigkeit, 

 Entwieklung und Vererbung vom Standpunkte der 

 Physiologie, " Jena, 1907. 



isms — such as the hand, the eye and many 

 others; but these always correspond to certain 

 constant features of the environment, and 

 play a part which in the last analysis is essen- 

 tially compensatory in the above sense. To 

 put the matter in somewhat different and more 

 general terms : if the characteristics of a sys- 

 tem undergoing perpetual change of composi- 

 tion and loss of energy are to be maintained 

 constant, it is indispensable that a set of proc- 

 esses antagonistic to and therefore compensa- 

 tory to these changes should be maintained. 

 The adaptive and regulatory, and most of the 

 " purposive " activities of an organism form 

 the conditions necessary to the existence of 

 these compensatory processes. Evidently, this 

 point of view implies a fitness in the environ- 

 ment as well as in the organism. The two 

 must correspond as lock to key — or as the 

 oppositely directed and mutually equilibrating 

 components of any system in equilibrium — if 

 any such interaction is to be possible. Hence 

 the continued existence of any organism im- 

 plies environmental fitness, i. e., the existence 

 of conditions and processes in the environ- 

 ment which correspond to or balance those in 

 the organism. It is thus inevitable, if we 

 consider the special peculiarities of any com- 

 plex and stable system, and correlate them 

 with those of the environment, that the latter 

 should be found to exhibit a " point for point " 

 and reciprocal correspondence with the for- 

 mer. The case of the organism has seemed 

 exceptional simply because biological students 

 have been so long accustomed to regard the 

 organism as a system possessing unique 

 " vital " properties and existing in an environ- 

 ment having totally distinct characteristics. 

 To the human mind there is no more profound 

 contrast than that between living and lifeless. 

 Dr. Henderson's study shows that even in its 

 ultimate constitution the environment pos- 

 sesses characters corresponding to those of the 

 living organism, and the discovery of this 

 truth will no doubt surprise many others, just 

 as it surprised him. But what if this were 

 not the case? Obviously, such systems as 

 organisms could never have come into exist- 

 ence. The surviving organic forms are simply 



