370 SERGIUS MORGULIS 



stimulus several times. In other words, the inhibition is cumu- 

 lative. Suppose the dog reacts to a familiar sound with 

 a secretion of nine — ten drops of saliva. A differentiated tone 

 calls forth no secretion, while the familiar sound produced im- 

 mediately afterwards causes this time a flow of seven — eight drops 

 of saliva. The experiment is then repeated with a modification, 

 the differentiated tone being now produced three times in 

 succession. The familiar sound is again applied, but this time 

 its influence is still more suppressed and only three — four drops 

 of saliva are obtained. 



Lastly, if differentiation is the result of inhibition, it is to be 

 expected that the finer the degree of differentiation attained the 

 greater would be the inhibition. The evidence in this respect 

 is also very favorable. If an auditory conditioned stimulus is 

 applied, then a sound one-eighth of a tone higher, the repetition 

 of the former, familiar stimulus exerts no influence on the salivary 

 gland. If, however, a sound one or several tones different is 

 employed, the conditioned salivary reflex to the familiar sound 

 remains now unaffected. This points very clearly to the con- 

 clusion that the finer the differentiation the more intense the 

 inhibition. 



It is a natural expectation that the inhibition or suppression 

 arises within the corresponding analyser. This can be shown to 

 be true by means of an experiment. If in the previous experiment 

 with the auditory conditioned reflex the familiar sound had been 

 associated with irrelevant stimuli of various kinds, it would have 

 been invariably found that neither visual nor olfactory nor any 

 kind of stimulus except auditory left an imprint upon the condi- 

 tioned reflex, showing that the inhibitory processes developed in 

 that analyser. 



The higher nervous processes are not stable but dynamic, 

 constantly changing, overflowing large territories in the nervous 

 system, then concentrating into narrow channels again. The 

 laws of radiation and concentration are even more strikingly 

 shown in the matter of inhibition. Starting in some one par- 

 ticular analyser the inhibitory process may radiate towards other 

 centres in the large hemispheres. The diffusion of the inhibitory 

 wave is apparent where the inhibitory process is experimentally 

 cumulated. Two conditioned reflexes, visual and auditory, may 

 be worked out in a dog. The introduction of a differentiated 



