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- 
