ANTS AND SOME OTHER INSECTS. 9 



live. They demand absolute exactitude and cannot understand 

 that such a thing is impossible. Besides, physiology has no reason 

 to pride itself upon the peculiar exactitude of its methods and re- 

 sults. 



Although we know that our whole psychology appears as the 

 activity of our cerebrum in connection with the activities of more 

 subordinate nerve- centers, the senses and the muscles, nevertheless 

 for didactic purposes it may be divided into the psychology of cog- 

 nition, of feeling and volition. Relatively speaking, this subdivi- 

 sion has an anatomico-physiological basis. Cognition depends, in 

 the first instance, on the elaboration of sense-impressions by the 

 brain ; the will represents the psycho- or cerebrofugal resultants of 

 cognition and the feelings together with their final transmission to 

 the muscles. The feelings represent general conditions of excita- 

 tion of a central nature united with elements of cognition and with 

 cerebrofugal impulses, which are relatively differentiated and re- 

 fined by the former, but have profound hereditary and phylogenetic 

 origins and are relatively independent. There is a continual inter- 

 action of these three groups of brain-activities upon one another. 

 Sense-impressions arouse the attention ; this necessitates move- 

 ments ; the latter produce new sense-impressions and call for an 

 active selection among themselves. Both occasion feelings of pleas- 

 ure and pain and these again call forth movements of defense, 

 flight, or desire, and bring about fresh sense-impressions, etc. 

 Anatomically, at least, the sensory pathways to the brain and their 

 cortical centers are sharply separated from the centers belonging 

 to the volitional pathways to the muscles. Further on in the cere- 

 brum, however, all three regions merge together in many neurons 

 of the cortex. 



Within ourselves, moreover, we are able to observe in the three 

 above-mentioned regions all varieties and degrees of so-called 

 psychic dignity, from the simplest reflex to the highest mental 

 manifestations. The feelings and impulses connected with self- 

 preservation (hunger, thirst, fear) and with reproduction (sexual 

 love and its concomitants) represent within us the region of long- 

 inherited, profoundly phyletic, fixed, instinct-life. These instincts 



