STRUCTURE AND FUNCTIONS OF THE CEREBRUM 189 



Since all our mental processes are dependent on language, im- 

 pairment of the language areas would be expected to lower the 

 whole mental power. This appears to be the case in most sufferers 

 from this condition. 



There is no evidence that any species of animals except the 

 human species possesses the power to use language. This differ- 

 ence sets man sharply apart from the animals most ^nearly ap- 

 proaching him in intelligence. 



Consciousness. This is a phenomenon that we all recognize 

 as existing in ourselves and as accompanying most if not all of 

 our cerebral activities. That it is present when the cortical cells 

 are actively functioning and absent when they are inactive is 

 indicated by the fact that any treatment, such as anaesthesia, 

 which depresses nerve-cells, tends to abolish consciousness. It 

 is a phenomenon whose nature is wholly unknown, and for whose 

 existence, even, there is no objective evidence. We cannot prove 

 that any lower animal has the same sort of consciousness that we 

 have. We can only suppose from the general similarity of their 

 cerebral processes to ours that this particular phenomenon is 

 also in them as in us. As we go down the animal scale where 

 mental processes become simpler and simpler does it follow that 

 consciousness becomes dimmer and dimmer? We ordinarily as- 

 sume this to be true, but without any positive evidence upon 

 which to base the assumption. 



Emotions. Another set of phenomena accompanying cerebral 

 activity, but known chiefly by subjective experience, are the 

 emotions. We knoW that certain sensory stimuli give us pleasure, 

 others arouse disgust. Love and hate, sorrow and joy, are mental 

 states which are associated with certain sense impressions im- 

 mediate or remembered. Emotion, like consciousness, does not 

 lend itself to objective study, and therefore does not come within 

 the realm of physiology beyond simple recognition of the exist- 

 ence of the phenomenon. It is true that emotional states are 

 usually accompanied by reactions of other parts of the body, the 

 blush which accompanies embarrassment being an example, but 

 this allows us only to judge whether an emotion is present, and 

 tells us nothing about its actual nature. 



Cerebral Functions Compared in Man and Animals. In the 

 higher animals as well as in man associative memory is the rep- 



