ARRANGEMENT OF STRUCTURAL ELEMENTS. 229 



controlling the outgoing impulses shall respond in due 

 order and with tempered force. 



Taking the nervous system as a whole, and for the 

 moment neglecting the manner in which its constituent 

 elements are grouped, it has been shown that the struc- 

 tural elements do not increase in size in proportion to 

 the size of the animal. Yet the spinal cord of a cat 

 would not suffice for a lion, nor that of a mouse for a 

 beaver, for in the cords of the larger animals, since the 

 individual cell-bodies are not so much larger, there must 

 be absolutely a greater number of cell elements as well 

 as great extension of the neuron to make up their bulk. 

 Not only is there an increase in the number of elements 

 representing the spinal nerves, but also in that of the 

 central cells and in any such series, the possible com- 

 binations theoretically increase far more rapidly than 

 the absolute number of the elements. These central 

 combinations rapidly increase with the increasing num- 

 ber of the central elements, though the number of them 

 is indeterminate, and probably variable. Nevertheless, 

 growth contributes to central complexity and organisa- 

 tion, and something will be gained by regarding the 

 matter from this side. 



