VASOMOTOR REFLEXES 359 



Cameron were inclined to believe. At any rate, the matter is 

 so importan: that we have repeated the experiments to test the 

 effects of respiration on blood-pressure. 



We have stimulated electrically the central stump of several 

 cut nerve trunks (saphenous, tibial, peroneal, sciatic, ulnar, and 

 median) with various strengths of stimulus. 



When the narcosis (with ether or chloroform) was not deep 

 enough, the respiratory movements were always increased by 

 strong stimulation. The most frequent response of the blood- 

 pressure to stimulation, e.g., of the sciatic nerve, may be illus- 

 trated bj^ figure 1. 



With weak stimulation there is practically no increase of res- 

 piratory movements either in amplitude or in frequency, and 

 the blood-pressure is either a fall or a fall followed by a more 

 or less marked rise. When stronger stimuli are applied, the re- 

 spiratory movements increase either in amplitude or in fre- 

 quency, or in both, and the blood-pressure rises, instead of 

 falling, and is followed by a marked fall. The rise of blood- 

 pressure increases usually in proportion to the development of 

 the strength of stimulation. 



In figure 2 the anesthesia was made much deeper with the 

 same animal as in figure 1, and stimuli of several strengths were 

 applied to the same nerve. 



There is very little increase of respiratory movements on each 

 stimulation, and the response of blood-pressure is also small in 

 degree. The latter, as seen from the figure, is either a fall or a 

 rise according to the strength of stimulation, and the marked 

 fall after the rise which is observed in figure 1 simultaneously 

 with the increased respiration cannot be seen. This suggests 

 at once that the marked fall accompanied by remarkably in- 

 creased respiratory movements might be ascribed, at any rate, 

 mainly, to the influence of the latter movements caused by sen- 

 sory stimulation. Moreover, under brain compression it is not 

 very difficult to stop the respiratory movements entirely, and in 

 this case only very strong stimulation will initiate spontaneous 

 respiratory movements. Under these conditions a fall of blood- 

 pressure of the same character as that observed with an in- 



