200 IRRITABILITY 



tation of fatigue, and this idea he defended with the greatest 

 tenacity for a long time, until finally, twenty-five years after, in 

 a treatise which he called "Abschied von der Ershopfungstheorie," 

 he renounced the idea as untenable. 



Among other investigations, which since this time have been 

 made to explain the mechanism of inhibition, those of Gaskell,^ 

 Hering" and Meltzer" have received widest consideration. These 

 theories are built upon the existence of the two phases of metab- 

 olism, and assume that inhibition, in contradistinction to dissimi- 

 latory excitation processes, depends upon an increase of the 

 assimilative processes. The principal evidence which Gaskell 

 advances is that when the vagus nerve of the tortoise heart, a 

 typical inhibitory nerve, is stimulated, a positive variation of the 

 demarcation current of the heart muscle occurs, whereas when a 

 motor nerve of a skeleton muscle is stimulated the attached muscle 

 shows a negative variation of the demarcation current. I must 

 confess that this explanation of inhibitory processes, from the 

 standpoint of an interpretation of processes in the living sub- 

 stance, seems very plausible, and I have accepted this even in my 

 address on excitation and depression before the Frankfurter 

 Naturforscher Versammlung.* I have since then endeavored to 

 obtain experimental evidence to substantiate this theory, in that 

 I attempted to prove that increase of the assimilatory processes 

 brought about by stimulation would be associated with a reduc- 

 tion of the specific irritability. For this purpose I have sought 

 for such cases in which a stimulus primarily and momentarily 

 increases assimilative processes in a system in a state of metabolic 

 equilibrium. I was disappointed, when, after years of investiga- 

 tion, I could not find such cases. There is only one kind of 

 stimulus of which we can say with positiveness that it primarily 

 increases the assimilative processes, that is, increased supply of 



1 Caskell: "On the innervation of the heart with especial reference to the heart of 

 the tortoise." Journ. of Physiology, Vol. IV, 1884. 



2 Ewald Hering : "Zur Theorie der Vorgange in der lebendigen Substanz." Lotos 

 IX. Prag 1888. 



3 Meltzer: "Inhibition." New York Medical Journal, 1899. 



4 Max Verworn : "Erregung und Lahmung. Vortrag gehalten in der allgemeinen 

 Sitz. der Gesellsch." Deutsch. Naturf. u. Aerzte zu Frankfurt a. M. 1896. Verb. d. 

 Ges. Deutsch. Nat. u. Aerzte 1896. 



