12 THE ORIGIN OF THE NERVOUS SYSTEM 



integration of a different order of magnitude from the 

 patterns of its constituent materials, whether these be 

 lumber, bricks, stone, or cement, and it is the orderly mass 

 arrangement of the material according to a certain 

 plan which constitutes the house. Similarly the organ- 

 ism represents a pattern which involves the orderly 

 arrangement and relation not of protoplasmic con- 

 stituents but of protoplasmic masses, cells, and organs. 

 In order to answer the question concerning the nature 

 of organismic pattern, and more particularly the possi- 

 ble role of quantitative factors in the origin and develop- 

 ment of this pattern, we must determine what the 

 different sorts of physiological organismic correlation 

 are, how they originate, and what part they play in 

 organismic integration. 



For present purposes it is convenient to group the 

 correlative factors under three heads: the mechanical 

 or contactual, the chemical or transportative, and the 

 dynamic or transmissive, and to inquire concerning the 

 possible role in integration of each of these groups. 



The mechanical or contactual factors include all 

 those which involve direct mechanical action, pressure, 

 or tension through direct or intermediary contact. 

 While they may play a part in determining size of 

 organs, direction of growth, or flow of fluids, and indi- 

 rectly, in certain cases, the irritability or metabolic 

 activity of protoplasm, it is difficult to conceive, in view 

 of the fact that the energy of living protoplasm is largely 

 chemical in origin, that they are primary or fundamental 

 factors in physiological integration. Moreover, in order 

 that they may act in a definite orderly way, differences 

 of some sort must already be present between the differ- 



