THE HISTORY OF THE SUBJECT 13 



based on the latter. They are only comprehensible then from 

 the unfoldings of cellular pathology. 



Until quite recently all those effects of external factors on the 

 living substance which consist in excitation, that is, in an increase 

 of their specific vital processes, have always stood in the fore- 

 ground of all researches and observations on irritability. It was 

 gradually, however, more and more recognized that the depress- 

 ing influence of stimuli played a great role in the vital process of 

 the organism. Brown was acquainted with exhaustion produced 

 by stimuli, and the discussion of "asthenic" diseases, in which the 

 irritability was reduced, occupied an important place in his path- 

 ology. That, however, in the normal activities of the organism 

 such depression or lessening of vital manifestation could result 

 from the influence of stimulation, first became clear after the 

 brothers Weber^ in 1846 discovered the inhibitory effects of the 

 galvanic stimulation of the vagus upon the heart. 



Since then the inhibitory processes in nerves have been fre- 

 quently investigated by Schiff (1833-1896), Goltz (1834-1901) 

 and others, who gave us a theory concerning the same. Only 

 a small number of inhibitory processes were known at that 

 time, as for instance the inhibition of the croak reflex of the 

 frog, or the inhibition of the grasp reflex during copulation 

 of these animals through skin stimuli, and a few other cases. 

 They regarded the inhibitory nervous processes as a special state, 

 of which the inhibition of the heart through the vagus was the 

 best illustration. Further, the Russian physiologist Setschenow 

 succeeded by directly stimulating certain parts of the central 

 nervous system, especially the optic lobes of the frog, in producing 

 inhibition. It was, therefore, frequently assumed, as Setschenow 

 did, that in the brain there exist special inhibitory centers, just 

 as there are motor centers. This view was later shown to be 

 untenable. It is only quite recently, and especially since Sherring- 

 ton has shown that inhibition plays a part in all antagonistic 

 muscle movements, that we have obtained a broad and more 

 thorough understanding of the inhibitory processes in the life 



1 Eduard Weber: "Muskelbewegung." Article in Wagner's Handworterbuch der 

 Fhysiologie, Bd. 3. Braunschweig 1846. 



