CONTRIBUTIONS FROM PAWLOW'S LABORATORY 365 



ditioned reflex may likewise be destroyed, leaving the others 

 unaffected, while total extirpation of the hemispheres results in 

 complete abolition of all conditioned reflexes. 



On the basis of these and many other facts, Pawlow regards 

 the hemispheres the seat of conditioned reflexes just as the 

 spinal cord is the seat of unconditioned, permanent, or inherent 

 reflexes. The large hemispheres, according to this view, are the 

 central station of the various analysers, both external, such as 

 the auditory, visual, etc., and internal, of which the locomotor is 

 the most important. 



By means of centripetal nerves from every articular surface, 

 tendons and muscle, each phase of the organism's movement is 

 signalized into the central nervous system where they frequently 

 combine with other organic functions. That this motor analyser 

 with its headquarters in the cortex of the hemispheres is just as 

 real as the tactile, olfactory and other external analysers is demon- 

 strated by the fact that it, too, can form conditioned reflexes. 

 Thus Krasnogorski could establish a salivary reflex to the move- 

 ment of the knee of the dog's hind leg. Every time the knee 

 was bent a secretion of saliva started in a reflex way. It was a 

 simple matter to prove that the conditioned reflex thus formed 

 was actually associated with an internal motor and not with an 

 external tactile stimulation, as might be supposed. If in a dog 

 with such a reflex to the bending of the leg, the gyrus sigmoidens 

 was excised the reflex immediately vanished, although a salivary 

 response to the stimulation of the skin still persisted. If, on the 

 contrary, the gyri coronarius and ectosylvius were removed, the 

 knee conditioned reflex could be obtained while the tactile reflex 

 completely disappeared. 



The all-important fact brought out by the experiments on 

 extirpating certain brain areas, namely, that the hemispheres are 

 the seat for the mechanism of conditioned reflexes and that the 

 destruction of definite regions is accompanied by loss of already 

 established conditioned reflexes or by an inability to form tem- 

 porary connections with those analysers whose central portion 

 has been impaired — this is the foundation for an entirely novel 

 interpretation of various psychic phenomena. The chief result 

 of its recognition is the substitution of a strictly objective 

 physiological point of view for an indeterminate psychological 

 thinking. The conception of psychic deafness or psychic blind- 



