28 



Memorial Number. 



can Physiological Society in 1889 and published in the New York 

 Medical Journal and under a different title in the Archiv. fiir 

 Physiologie he describes experiments intended to show that two 

 kinds of afferent fibers exist in the vagus nerve, one exciting and the 

 other inhibiting inspiratory movements. He used this fact to 

 modify the Hering-Breuer theory of the self-regulation of the 

 respirations by assuming that the expansion of the lungs stimulates 

 both groups of fibers. The resultant effect, as in the case of the 

 simultaneous stimulation of the motor and inhibitory fibers to the 

 heart, is a dominance of the inhibitory effect, thus cutting short the 

 inspiration and bringing on an expiration. But after the inhibi- 

 tion ceases the excitatory fibers, which, like the accelerator^ 

 fibers of the heart have a long after action, come into play and 

 start a new inspiration. In his first general paper on inhibition 

 this idea of a combined action of opposing processes is extended 

 by the citation of numerous instances taken from physiological 

 literature and is expanded into a general theory which makes 

 inhibition a universal property of irritable tissues. 



"I entertain and defend the view that the phenomena of life 

 are not simply the outcome of the single factor of excitation, but 

 they are the result of a compromise between two antagonistic 

 factors, the fundamental forces of life, excitation and inhibition." 



That is to say, whenever a tissue is stimulated two different 

 processes are aroused, one leading to functional activity and one to 

 a suppression of activity. As to the nature of these processes very 

 little is said. He was not satisfied with the Hering-Gaskell con- 

 ception that excitation follows or is an accompaniment of catabolic 

 changes while inhibition is due to processes of an anabolic or 

 assimilative character. He goes only so far as to assume that 

 both processes are concerned with the kinetic and potential energies 

 of the system, that excitation facilitates the conversion of potential 

 to kinetic energy while inhibition hinders or retards this con- 

 version, like the turning off or on of a stopcock. Nor was he 

 satisfied with Sherrington's term of reciprocal innervation to 

 describe all of the phenomena he had in mind. While this phrase 

 is a suitable designation for the relationship between physically an- 

 tagonistic muscles such as the flexors and extensors it is less ap- 

 propriate in other cases, for example the simultaneous phases of 



