364 D. OGATA AND SWALE VINCENT 



are inclined to believe that a greater number of pressor re- 

 sponses could be obtained if we could improve the method of 

 stimulation so that the sensory fibers might be stimulated more 

 strongly. 



It thus appears from our experiments that the depressor effect 

 of weak stimuli is much more common than Vincent and Cam- 

 eron thought, though these observers were careful not to deny 

 its occurrence. Reid Hunt/'' in a recent paper, seems to have 

 had the same difficulty that Vincent and Cameron encountered 

 in obtaining the depressor effect of weak stimulation, which he 

 ascribed to the different frequency of stimulation they employed. 



The fact that a weak stimulation of a sensory nerve causes, 

 as a rule, a reflex fall of blood-pressure and a strong stimulation 

 a reflex rise, together with the statement of Bayliss^ that the 

 orthodox effect due to the stimulation of the depressor nerve 

 (nerve of Cyon^) can be converted into a rise by the action of 

 strychnine, led us to inquire whether a pressor response could 

 be obtained by strong stimulation of the depressor nerve. So far 

 as our results inform us, neither such a strong current as would 

 injure the nerve nor induction shocks up to eighty per second 

 frequency could reverse the depressor response. The response 

 to the stimulation after injection of strychnine was sometimes 

 increased and sometimes decreased, but the reversal of the re- 

 sponse did not appear in our experiments even with a dose 

 which caused general convulsions on weak stimulation. 



4. THE INFLUENCE OF THE FREQUENCY OF STIMULATION UPON 



VASOMOTOR REFLEXES 



That the frequency of stimulation has a certain effect upon 

 vasomotor reactions seems to have been known to the older in- 

 vestigators. In 1883 Kronecker and Nicolaides'-" noticed that the 

 vasomotor centers could more easily be affected by changing the 

 frequency of stimulation than by changing its strength. They 

 write: ''One can never attain such a strong vasoconstriction by 

 increasing the intensity of the stimulating current as by increas- 

 ing the frequency of the current of moderate .ntensity." We 

 have not been able to consult the original paper of these writers. 



