THE PROBLEM OF PATTERN 13 



ent regions or parts concerned, or the differences must 

 arise through the direct local action of some external 

 factor. The role of these mechanical factors is mani- 

 festly secondary and incidental and is limited to organ- 

 isms in which pattern of some sort has already been 

 established and is in process of development. 



Chemical correlation, so called, perhaps more properly 

 transportative correlation, includes the movements and 

 exchanges of substance between the various parts of the 

 organism. The internal secretions, hormones in general, 

 and also the movements and exchanges of nutritive sub- 

 stances, water, electrolytes, and waste products of metabo- 

 lism, fall under this head. Transportative correlation, 

 in short, includes the material exchanges and movements, 

 the commercial relations, so to speak, within the organ- 

 ism. These transportative factors in organismic cor- 

 relation are obviously of great importance, and the work 

 of recent years upon the more highly specialized aspects 

 of such correlation, the internal secretions, hormones, 

 etc., has shown us the bewildering variety and com- 

 plexity of this kind of correlation in the higher animals. 

 Moreover, when we consider that every organ is to some 

 extent and in some way concerned in transportative 

 correlation and that such correlation plays an essential 

 part in the growth, differentiation and maintenance of 

 the various organs, its significance in organismic inte- 

 gration becomes sufficiently obvious. 



The question at once arises whether transportative 

 correlation is the primary and fundamental factor 

 in organismic integration. A moment's consideration 

 shows that the existence of definite and orderly trans- 

 portative correlation implies the existence, first, of 



