272 THE NERVOUS SYSTEM 



apply his mind to the act of walking or standing; his mental 

 faculties may be as completely engaged with the deepest thoughts 

 of psychology, literature, medicine or other subjects while walk- 

 ing as at any other time. True, he probably started with some 

 fixed purpose to go in some particular direction to some definite 

 place, but the act of progression does not per se require fixed at- 

 tention on his part. So in the case of the pigeon; it does not, 

 make up its mind to fly at all; and it will not fly without being 

 thrown into the air, or the application of some other similar 

 stimulus; nor does it fly in any particular direction, or to any 

 particular place. It is reduced to the condition of a " mechan- 

 ism without spontaneity." It can perform voluntary move- 

 ments but cannot originate them without external inter- 

 vention. 



Animals which have been subjected to the operation men- 

 tioned undoubtedly feel pain. They move away or cry out on 

 being burned, for example. The coordination of their move- 

 ments and the cries contrast with the phenomena (reflex) fol- 

 lowing such stimulation when only the cord is left. It was noted 

 above that impressions in these cases are probably received by 

 the gray matter of the pons and not recorded. 



The special senses of sight and hearing remain after the re- 

 moval of the cerebrum. The same is probably true of taste and 

 smell. 



It would seem that the cerebrum is a kind of storehouse in 

 which are kept all the materials necessary for the performance 

 of all kinds of pre-determined acts, whether they manifest them- 

 selves in speech, or thought, or muscular action. What excites 

 these materials to activity i. e., what excites a voulntary act 

 is not clear. We know certain things will usually excite a certain 

 train of thought, or cause us to will to do or say certain things. 

 Such phenomena are akin to, if not identical with, reflex action. 

 These manifestations of our voluntary power are due to impres- 

 sions conveyed by afferent fibers to the cortex; indeed it may 



