480 COMPARATIVE PHYSIOLOGY. 



but tlie inferences thus drawn have been modified and supple- 

 mented by the results of experiments on certain other mam- 

 mals. 



It is especially important to bear in miud that, while certain 

 conducting paths are usual, they are not invariable: in like 

 manner, reflex impulses may not be confined to usual groups of 

 cells, but may extend widely, and so bring into action a large 

 number of muscles. The resulting reflex in any case is depend- 

 ent on the character, intensity, and location of the stimulus, 

 and especially on the condition of the central cells involved. 

 In the whole functional life of the cord the influence of higher 

 centers in the organ itself and especially in the brain is to be 

 considered. The cord is rather a group of organs than a 

 single one. 



