48 



BRAINS OF RATS AND MEN 



CENTER 



axon forms a final common path for all of them. In 

 man there are in the midbrain and thalamus separate 

 centers for all of these systems, and their integration 



is effected by a much more 



TIC t 



^NTER complex apparatus, a part 

 of which is in the cerebral 

 cortex. In the Amphibia 

 much simpler mechanisms 

 are found in the midbrain 

 for summation of stimuli 

 of diverse sorts and doubt- 

 less for various inhibitions 

 Fig. 3.-Diagram of a cross- fj-om Conflict of sensory im- 



section through the midbrain of , i r i • i 



Necturus, illustrating a single P"'^" ^^^ of these With 



correlation neuron of the mid- mnemonic veStigeS of pre- 



brain roof. One dendrite spreads vious experience; but there 



out in the optic center among jg imperfect provision 



terminals of the optic tracts; an- r -i r r 



other dendrite similarly spreads ^f ^^e apparatus for funC- 



out in the acoustic and tactile tionally Separated reflex 



center. From Herrick (1913); for connections with cleaHy dc- 

 the details of this apparatus see r i 1 r .♦ 



„ . , , V ^^ lined localization in space 



adapted for diversified spe- 

 cific responses to particular kinds of excitation. The 

 movements, though of a very precise character of 

 high adaptive value, are still largely on the plane of 

 total reactions to a general situation, rather than 

 diversified movements, each of which is in response 

 to some particular factor in the stimulus complex.' 



*0n the behavior of Necturus see Whitman (1899, p. 295), Eycle- 

 shymer (1906), Reese (1906), and Sayle (1916). 



