THE MASTER CONTRIVANCE 239 



hemispheres, near their hinder or occipital poles. The 

 machinery is represented by the cortical areas of the 

 occipital regions. The area on the right hemisphere 

 registers the field of vision which lies to the left side of 

 the middle line of the face ; the left hemisphere, the field 

 of vision to the right of the middle line. Then imme- 

 diately in front of the registering areas are those for the 

 interpretation or comparison of the messages received by 

 the registering areas. Still further forwards are the 

 administrative areas of cortical operatives, the position 

 of those for the left hand and arm being indicated in 

 fig. 45, A. In the same illustration are indicated the 

 cortical areas which carry on the registration and inter- 

 pretation of sound waves, areas which are thrown into a 

 state of great activity when we listen to learned lectures. 

 It is by the invention of an elaborately contrived cortical 

 mechanism that Nature has given the human brain the 

 power to see, hear, think, and act ; countless myriads of 

 microscopic operatives carry out the functions of both 

 remembrancer and judge. They constitute the spheres 

 of pure intellectual activities. 



The great cortical fields (of the cerebrum) represent 

 the highest flights of Nature's inventive genius. Prof. 

 Elliot Smith has made it very clear to us that the capacity 

 of an animal to learn new movements or acts depends 

 on the extent and quality of the cortical areas. In the 

 brains of anthropoid apes we see the overgrowth of 

 cortical areas which culminates in the enormous develop- 

 ment attained in the human brain. Without these cortical 

 fields, as Dr Henry Head has proved in recent years, 

 we should know nothing of time or of space. The nerve 

 centre or grey substance of the cerebrum, however, are 

 not all spread out in its cortex. Deep within the hemi- 

 spheres, forming swollen enlargements at the root of 

 the brain stem, are two great masses of grey nerve 

 substance. These masses represent the great receiving 

 stations which deal with the continual incoming flood 

 of messages which give us our feeling of comfort or 

 discomfort, of pleasure or pain, messages which make us 



