CHAPTER XXIII 



UNCOVERING THE MACHINERY OF THE BRAIN 



From very ancient times the kind of work done by the 

 brain was known. It was a matter of common experi- 

 ence that when a man was struck a severe blow on the 

 head he immediately lost control of all his muscles and 

 fell down in a heap ; he could no longer speak, see, hear, 

 or feel ; he became unconscious. Men in ancient times 

 therefore concluded that the brain, which fills the skull 

 and is injured when the head is struck, was the seat of 

 consciousness and of the will. 



The ancients also knew that nerves were the pathways 

 by which the brain could communicate with the trunk 

 and limbs. They observed, when the nerves to a limb 

 were divided, that the limb could no longer be set in 

 motion by the will ; nor, when such a limb was touched 

 or injured, could any message be transmitted to the 

 brain. In these earlier times the fibres of nerves were 

 supposed to be minute pipes containing a fluid which 

 served to convey messages to and from the brain. Every 

 nerve pipe was supposed to be capable, as is a telegraphic 

 wire, of conveying messages in either direction — to the 

 brain or from it. The brain itself was regarded as a 

 factory of animal spirits which flowed out into the body 

 and returned within the nerve pipes. Such a theory gave 

 the ancients a satisfactory explanation of why nerves were 

 sent out from the brain and spinal cord to every part of 

 the body. The nervous system was a means of endowing 

 the body with animal life. 



In less than twenty years Harvey blew the ancient 



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