x THE FORE-BRAIN 623 



functions of the auditory and visual sphere of the dog, affords 

 new evidence in support of this hypothesis. He educated certain 

 dogs to swallow pieces of meat only on hearing a given sound, 

 and not to touch them at sounds of a different pitch. These 

 animals retained the capacity for recognising the " dinner-sound " 

 even when the cortex of both temporal lobes had been destroyed. 

 This shows according to Kalischer that these complex reactions 

 (which certainly cannot be identified with simple reflex acts) may 

 take place in the absence of the sensory auditory area, provided 

 the subcortical auditory centres are present and are functionally 

 Intact. 



Kalischer taught other dogs to touch their food only in 

 brilliantly lighted surroundings, and not to take it in a dim light. 

 This habit was also preserved after removal of both occipital lobes 

 (Munk's visual sphere), proving, according to Kalischer, that the 

 power of recognising differences of luminous intensity does not 

 depend on integrity of Munk's cortical visual centres. On the 

 other hand, the power of recognising differences in colour depends 

 on the integrity of the cortical visual sphere. Kalischer showed 

 in a recent series of experiments (1909) that dogs that were 

 accustomed to take pieces of meat only when light of a given 

 colour, e.g. red, was let into the room, and not to touch them when 

 the light was a different colour, entirely lost the power for recog- 

 nising the " dinner-colour " after removal of both occipital lobes. 



These ingenious experiments should be controlled. They do 

 not controvert the generally accepted theory that the highest 

 mental functions of perception, memory, association, are seated in 

 the sensory spheres of vision and hearing. They rather tend to 

 support the hypothesis that these spheres are not sharply limited 

 to the cortex of the temporal and occipital lobes, but extend 

 upward and forward towards the parietal lobe. 



Experimenting with monkeys, Horsley and Schafer confirmed 

 the predominating importance of the posterior regions of the 

 hemispheres in relation to psychical functions. They stated that 

 a condition of idiocy was more readily produced in the ape by 

 removing extensive regions of the temporal lobes on both sides 

 than by cutting off the pre-frontal region completely by an incision. 



The most striking evidence of the psychical importance of 

 Flechsig's posterior association area is, however, derived from 

 clinical and anthropological observations. Clinical data show 

 that external lesions of the cortex, particularly if bilateral, are 

 capable of producing mental disorders or diminution of intelligence, 

 whatever their situation. But it is a fact that the most common 

 and serious of such disorders depend on lesions localised in this 

 area. Failure of the ideative faculty, mental confusion, dementia, 

 obvious symptoms of psychical blindness and deafness, are more 

 or less characteristic symptoms of bilateral destructive lesions of 



