THE CONTROL OF THE CIRCULATION 



245 



more and more marked elevation of blood pressure through, a very long 

 range of stimuli. Cooling or partial degeneration of the nerve makes it 

 hyper excitable to depressor reflexes so that these occur whatever strength 

 of stimulus is used. 58 



Stimulation of two afferent nerves at the same time usually produces 

 a greater reflex vasomotor change than the stimulation with an equiva- 

 lent strength of current of either nerve alone. That is to say, the effect 

 produced by stimulating the central end of both sciatics simultaneously 



fig. 74. The effect of strong stimulation (heat) of the skin of the foot on the arterial blood 

 pressure and respiratory movements. Upper tracing, thoracic movement; lower tracing, arterial 

 blood pressure. 



will be greater than that produced by stimulating either alone with double 

 the strength of stimulus. 



As has been stated above, the reflex change in blood pressure is often 

 quite transitory in nature, although the stimulation of the pressor nerve is 



