344 THE BODY AT WORK 



stimulation of certain areas of the cortex of the cerebrum 

 of an animal under the influence of an anaesthetic, and there- 

 fore incapable of voluntary action, induces definite movements. 

 Although the surgical applications of this discovery have 

 proved immensely important, its physiological value, as afford- 

 ing a method of investigating the functions of the brain, is ex- 

 tremely small. Yet the discovery gave an impetus to the 

 further study of the cortex, which has been rewarded with 

 many exact results. By the discovery of its excitability to 

 electric currents it was proved that the whole cortex has not 

 exactly the same work to do, or perhaps this is the safer 

 form of statement does not do its work in exactly the same 

 way. As soon as it was known that it is divisible into areas 

 differing in function, many methods by which the delimitation 

 of the areas might be attempted were devised. The converging 

 efforts made during the past forty years by comparative 

 anatomists, histologists, physiologists, pathologists, and phy- 

 sicians, have resulted in the acquisition of an accurate, if very 

 restricted, understanding of the construction and mode of 

 working of the apparatus of thought. Of some of the new 

 data the psychologist is able to make use ; but so far as the 

 physiologist is concerned, it is the vehicle of mind which is the 

 subject of study, not its contents. 



A new subject has been created since 1870. There is there- 

 fore nothing to be gained, so far as our present purpose is con- 

 cerned, from the consideration of views which were current 

 before that date ; and sin,ce, as must always occur when a 

 science is rapidly advancing, observations which logically 

 should have been the first to be made were not thought of 

 until it became necessary to devise methods of checking results 

 obtained in other ways, we will consider the various sources 

 of our information without regard to the chronological order 

 in which they were opened up. 



The cerebral hemisphere contains two large central masses of 

 grey matter, the nucleus caudatus and the nucleus lenticu- 

 laris, often described as a single structure under the name 

 " corpus striatum." Their functions are unknown. The 

 nerve-fibres which connect the cerebral hemispheres with the 

 rest of the central nervous system form two thick limbs or 

 crura on tl^e under side of the brain. Each crus turns upwards 



