ORIENTATION AND FUNCTION 167 



flexors produce more energy, in the legs of the left 

 side the extensors. The transverse current assists the 

 animal in moving to the right toward the anode and 

 prevents it from moving to the left toward the kath- 

 ode. Hence the nervous elements which produce 

 the sidewise movement of the crayfish toward the 

 right must have the opposite orientation in regard to 

 the longitudinal axis from the nervous elements which 

 produce the sidewise movement to the left. 



Maxwell and I had attempted to give a picture of 

 the arrangement of those elements on the assumption 

 that they are the motor neurons. No reason exists, 

 however, for regarding the ganglion-cell in toto as the 

 point of action for the chemical effect of the ions set 

 free. It may be any element inside of the ganglion- 

 cells, or even of the fibre itself ; it is not even neces- 

 sary that this element should be especially noticeable 

 histologically. Life-phenomena are determined by 

 physical and chemical conditions which are outside the 

 realm of histology. But whatever it is, it is certain 

 that those determinative elements in the central ner- 

 vous system whose activity produces movements of the 

 body, have a fixed orientation in the body, which evi- 

 dently stands in some simple relation to the direction of 

 the movement whicJi is produced by it. 



The idea of such a simple relation between the 

 orientation of nervous elements and the direction of 

 motion produced by them is no more strange than 

 the facts observed in the stimulation of the horizon- 

 tal canal of the labyrinth. If this canal be slightly 



