THE CENTRAL NERVOUS SYSTEM 695 



a wound of the grey or white matter, may cause a stimulation of 

 nervous tracts by which, for a time, the * deficiency ' effects of the 

 lesion may be masked. 



In the fourth place, we must not hastily conclude that when no 

 obvious deficiency seems to follow the removal of a portion of the 

 central nervous system, the function of that portion must necessarily 

 be of such a nature as to give rise to no objective signs. For we 

 have reason to believe that, to a certain extent, the function of one 

 part may, in its absence, be vicariously performed by another. 



Bearing in mind the cautions we have just been empha- 

 sizing, we may broadly distinguish between the functions of 

 the cord (including the bulb) and those of the brain proper 

 by saying that the cord is essentially the seat of reflex 

 actions, the brain the seat of automatic actions and con- 

 scious processes. But neither of these conceptions is 

 entirely correct. Both err by defect and by excess. The 

 brain, it is true, is pre-eminently automatic. The move- 

 ments which are started in the grey matter of the cerebral 

 cortex are pre-eminently voluntary (p. 739), but we cannot 

 deny to the brain the possession of reflex powers as well. 

 The movements in which the only nerve centres concerned 

 are those of the spinal cord are above all reflex (p. 704). 

 But some of its centres, and especially those lying in the 

 medulla for example, the respiratory centre are perhaps, 

 much as they are influenced by afferent impulses, capable of 

 discharging automatic impulses too. And while conscious- 

 ness is certainly bound up with the integrity of the brain, 

 and in all the higher mammals is probably associated with 

 cerebral activity alone, it has been plausibly maintained 

 that the spinal cord, even of such an animal as the frog, is 

 also endowed with something which might be called a kind 

 of hushed consciousness. If this is so for the frog, with its 

 distinct though relatively ill-developed cerebral hemispheres, 

 it must be still more likely in the case of fishes and animals 

 below them, which are practically devoid of a cerebral cortex 

 altogether. 



