VASOMOTOK REFLEXES 



89 



the bulb acting on heart via efferent cardio-inhibitory fibres in the opposite 

 uncut vagus. If there is no cardiac inhibition the fall of pressure may 

 be preceded by a small rise of pressure. The fall of mean arterial pressure is 



'^^^^^mm^, 



TexT'FIg. 34. Carotid-pressure record showing pressor reflex evoked from afferent nerve ; 

 decerebrate preparation (J. H. Mather and C. S. S.). a.p., carotid pressure by Hg manometer ; 

 z, abscissa-line of arterial pressure ; t, time in 6" intervals ; e, signal-line showing duration 

 of the faradization of the central piece of the severed peroneal nerve. Curare had been given to 

 obviate reflex movement of the skeletal muscles, but this is not necessary. 



due partly to the cardiac inhibition (an effect already studied by you in exerc. 

 V), and partly to afferent fibres which, like those in the depressor branch, 

 exert a depressor influence upon the tonic activity of the vasomotor centre 

 in the bulb. 



2131 N 



