140 nil-: XKKVui's s VST KM AND ITS CONSERVATION 



but it is evident that cutting all the wires at various 

 places would have the same crippling effect. This is a 

 fair analogy to help one to understand the present con- 

 c.-ption of the cortical centers. They are not believed to 

 originate impulses, excepting as impulses come to them; 

 their peculiarity is found in the fact that in them a vast 

 number of neural arcs of correlated function are brought 

 so close together as to be readily subjected either to 

 stimulation or to damage. 



This may be maintained as well for other areas of the 

 brain as for the motor regions. For example, certain 

 portions of the cortex at the back of the cerebrum, par- 

 ticularly where the surface of each hemisphere is infolded 

 and lies against the surface of its fellow, are held to be 

 visual centers. It is reported that injury to these fields 

 impairs the usefulness of the eyes and, if sufficiently ex- 

 tensive, causes complete loss of sight. These are regions 

 which visual impulses enter after having been relayed by 

 the midbrain structure-, and they are regions from which 

 impulses are normally sent away to other pails of the 

 brain so that other actions may be modified as a result of 

 the inflow from the eyes. To destroy such areas (on both 

 sides) is to destroy useful vision, but it is really a system 

 of pathways which has been interrupted and not a reposi- 

 tory of visual impressions. 



If we reduce all the activities of the cerebrum to elabo- 

 rated reflexes and, as such, demand for them external 

 causation, immediate or past, what becomes of freedom 

 of the will? This is a troublesome and unwelcome 

 (jiiestion which different thinkers have answered in 

 different fashion. It may be thought to lie outside the 

 proper sphere of the physiologist, but it confronts him 

 when lie becomes a teacher of hygiene. It haunts every 

 man of science, as it has haunted theologians and philos- 

 ophers of all ages. Many have been brought to the essen- 

 tial position of .Jonathan Kdwards, which was, in brief, 

 the view that we are free to do what we will, but not to 

 will what we shall do. Candid scientists often admit 



