266 COMPARA TIVE PHYSWLOG Y OF THE BRAIN 



processes as involve the right fore-leg. In our opinion, 

 the phenomena observed by Hitzig are the outcome of 

 a weakening of certain groups of muscles and a diminu- 

 tion of the sensibility in the right leg. Such disturb- 

 ances could just as well be produced by a pressure 

 upon certain peripheral nerve-fibres. 



That Hitzig's psychological interpretation of his 

 observation is wrong has been proved by Goltz. If 

 Hitzig's idea were correct, we ought to assume that, if 

 the centre of the right fore-leg were removed, a dog 

 should no longer be able to use the right paw as a 

 hand, where such a use is based upon the activity of 

 associative memory. Goltz not only removed the 

 centre but the entire left hemisphere of a dog that 

 had been taught to dig its food out of a heap of 

 pebbles. This dog showed all the disturbances of 

 the right leg which Hitzig described. Yet it con- 

 tinued to dig its food (pieces of meat) out of the 

 heap of pebbles with the right fore-paw. It preferred 

 to use the left paw for this purpose. But when this 

 was forbidden it used the right paw with success. 

 This experiment proves that the conscious or psy- 

 chical character of the motions of the fore-leg is not 

 affected by the removal of its cortical centre. A close 

 observation of the way the dog uses this paw shows 

 that certain muscle-groups must have suffered by 

 the operation, and a closer analysis of these purely 

 muscular disturbances explains the anomalies which 

 Hitzig had mistaken to be of a psychical character. 

 Removal of the fore-leg centre causes a decrease in 



