284 MANUAL OF PHYSIOLOGY. 



AFFERENT CARDIAC NERVES. 



Besides these nerve channels bearing impulses to the heart, 

 others pass from the heart to the medulla, probably having their 

 origin in the inner lining of the heart, which is known to be the 

 part most sensitive to stimulus. 



These fibres appear to be of two kinds, one of which affects 

 the cardio-inhibitory centre and diminishes the pulse rate ; the 

 other affects the vaso-inhibitory centre and lowers the blood 

 pressure. Increase of the intra-ventricular pressure stimulates 

 both these sets of fibres, and thus we see that over-filling of the 

 heart from increase of blood pressure, etc., causes retardation of 

 its beat, and an equilibrium is thus established between the gen- 

 eral blood pressure and the force of the heart beat. 



