Vol. XXXIX. September, 1920. No. 3 



BIOLOGICAL BULLETIN 



SOME CONSIDERATIONS CONCERNING THE 

 NATURE AND ORIGIN OF PHYSIOLOGICAL 



GRADIENTS. 



C. M. CHILD. 

 (From the Hull Zoological Laboratory, the University of Chicago.) 



AUTHOR'S ABSTRACT. 



The paper is a survey of the evidence bearing upon certain aspects of the 

 problem of integration or pattern in organisms. The organism represents a 

 definite pattern or integration of some kind. The pattern of the organism is 

 of a higher order of magnitude than protoplasmic pattern since it involves 

 masses of protoplasm or even cells each of which may possess the entire pro- 

 toplasmic or cell pattern. Protoplasm apart from environment does not appear 

 to possess any inherent mechanism for originating such pattern. 



While specific differences appear in the development and differentiation 

 of pattern in each organism, in its more general features such as polarity and 

 symmetry, this pattern appears to be largely independent of specific differences 

 in protoplasmic constitution. This fact suggests that it represents primarily 

 a non-specific or quantitative condition or relation in a specific protoplasm. 



Many different lines of evidence which are briefly reviewed indicate, first, 

 that the simplest form of axiate pattern is primarily a gradient in physiological 

 condition, involving the fundamental metabolic reactions as well as various 

 other factors, and second, that such gradients arise in the final analysis from 

 differential exposure to external factors which affect the rate of protoplasmic 

 activity. The primary physiological relations established in this way are 

 those of excitation and transmission but from the first moment of differentia- 

 tion chemical or transportative correlation becomes possible and plays an 

 increasingly important role in the progress of development. 



The living organism is manifestly not simply a fortuitous 

 aggregation of substances but represents an order or unity, an 

 integration of some sort, and the problem of the nature of this 

 order and unity, the problem of organismic integration 1 is one of 



1 In view of the fact that the word " organism " which implies the exist- 

 ence of a unity and order in the entity so designated is universally accepted- 

 and employed, the word " organismic " is not only biologically and etymologic- 

 ally justified, but fills a need which is becoming more and more apparent. 



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