4 THE ORIGIN OF THE NERVOUS SYSTEM 
wooden material, become possible when the materials 
are steel or concrete. Protoplasm in consequence of its 
physicochemical constitution represents a certain kind 
of material in which certain kinds of pattern are possible, 
and organismic pattern must lie within the range of 
possibilities determined by this constitution. 
As regards the most minute and presumably the 
simplest organisms, e.g., certain bacteria and ultra- 
microscopic forms, if such exist, our knowledge is at 
present insufficient to permit us even to say with cer- 
tainty whether they are cells in the ordinary sense of 
the word, and concerning their pattern as organisms 
we are almost completely ignorant, but it is at least 
certain that in the bacteria orderly differences between 
surface and interior exist. The single cell is of course 
primarily an organism, though it may as a part of a 
multicellular organism become specialized and lose to a 
greater or less degree its capacity for independent exist- 
ence. And, finally, the multicellular form represents a 
still more complex order and integration. 
ORGANISMIC PATTERN 
The fundamental fact for present purposes is that 
the organism, as the term implies, represents an order 
and unity of some sort. Concerning the character of 
this order in the simplest living forms we know practi- 
cally nothing, but as regards all other organisms we may 
say that this order expresses itself in the appearance of 
more or less definite spatial morphological and functional 
relations and in a more or less definite and orderly 
behavior of the whole. It is necessary before going 
farther to inquire how the organismic pattern or order 
