CONTRIBUTIONS FROM PAWLOW'S LABORATORY 373 



This very interesting question of the secondary conditioned 

 reflexes is, however, still in the initial stages of investigation. 



Thus from the objective, physiological point of view ' this 

 seemingly chaotic and infinitely complex, ever-changing reaction 

 of the organism to the flux of countless influences of the outer 

 world, in a word, all that is commonly called psychic activity, is 

 nothing but an endless chain of reflexes, i.e., determined responses 

 to the environment. The kaleidoscope of conditioned reflexes in 

 its fantastic and apparently irregular and undefinable play in 

 reality is controlled by rigid laws, by the intensity, duration and 

 direction of the nervous processes in the large hemispheres." 



In the foregoing two remarkable facts have been mentioned 

 in passing, the further discussion of which has been purposely 

 deferred until this moment. It will be recalled that a noise 

 produced during an experiment, which excited the animal, caused 

 simultaneously the disappearance of a previously established 

 differentiation. If the dog could recognize one-eighth of a tone 

 it would now, under the excitement, give the conditioned salivary 

 reflex to any sort of auditory stimulus. Psychologically speak- 

 ing, the animal was in a state of affectation. Physiologically, 

 the strong irritation radiated over a large territory in the brain 

 and so affected the tonus of its nervous elements that all signs 

 of inhibition were temporarily masked. 



It will further be recalled that the experience of workers in 

 this subject is that no matter how persistently one may try it is 

 impossible to work out a conditioned reflex to any factor what- 

 soever if the physiological stimulus (food) is employed before the 

 stimulus, which it is desired to make a conditioned stimulus, is 

 used. On the contrary, if such a stimulus is followed up by the 

 physiological stimulation a salivary reflex is created very speedily. 

 To understand this fact it must be regarded in the light of the 

 general statement — as given above — that a heightened state 

 of irritability in one part of the cortex lowers the susceptibility 

 of adjacent parts, and that the stronger the irritability the wider 

 the range of its influence. 



Here are a few other similar instances. A watch dog of a 

 highly nervous temperament with a well formed conditioned 

 reflex is the subject of an experiment, which is to be conducted 

 by a stranger. The appearance of this stranger in the laboratory, 



