CHAPTER VIII 



INTERFERENCE OF EXCITATIONS 



Contents: Examples of effects of interference of stimuli in unicellular 

 organisms. Interference of galvanic and thermic stimuli in Para- 

 mecia. Interference of galvanic and thermic stimuli and narcotics. 

 Interference of galvanic and mechanical stimuli. Interference of gal- 

 vanotaxis and thigmotaxis in Paramecia and hypotrii infusoria. Real 

 or homotop interference, apparent or heterotop interference. The 

 two effects of homotop interference of excitations : Summation and 

 inhibition of excitations. Theory of the processes of inhibition. 

 Hering-Gaskell theory. Inhibition as an expression of the refractory 

 period. Individual possibilities of interference of two stimuli. Inter- 

 ference of an excitating and a depressing stimulus. Interference of 

 two depressing stimuli. Interference of two excitating stimuli. 

 Analysis of the interference of two excitations. Interference of two 

 single stimuli. Conditions upon which the result of interference is 

 dependent. Heterobole and isobole living systems. Intensity of the 

 two stimuli. Interval between the stimuli. Specific irritability and 

 rapidity of reaction of the living system. Latent period. Interference 

 of single stimuli in a series. General scheme of the development of 

 the effect of interference. Summation and inhibition. Apparent 

 increase of irritability. Conditions of summation. Tonic excitations. 

 Conditions of inhibition. Various types of inhibition. Interference 

 of two series of stimuli. Relations in the nervous system. Peculiari- 

 ties of the nerve fibers. Conversion of the nerve by relative fatigue 

 from an isobolic into a heterobolic system. 



Until now the mechanism of the single excitation has received 

 the major portion of our attention. It was not until we reached 

 the subject of the origin of fatigue that we became acquainted 

 with the effects of repeated stimulation. Here we found a case 

 of interference of individual excitations. But fatigue is simply 

 a special instance of such interference, for the subject of inter- 

 ference action occupies a much greater field. 



Every cell of the larger organisms, and more especially the 

 single celled organisms, is subjected to manifold stimuli. It is 



