THE CARDIAC NERVES. 545 



on the heart, and that its rate is the resultant or algebraic sum of 

 their effects, and that sudden changes in this rate, such as result 

 from sensory or psychical disturbances of any kind, may be referred 

 to a reflex effect upon either the cardio-inhibitory or the accelerator 

 center. While physiology has demonstrated the general properties 

 of the regulating nerves of the heart, the inhibitory, on the one 

 hand, and the accelerator and augmentor on the other, it is necessary 

 for much more work to be' done in order to explain satisfactorily 

 how these nerves participate in the various normal and pathological 

 changes of rate and force of beat. 



The Accelerator Center. The accelerator fibers arise primarily in 

 the central nervous system. Since stimulation of the upper cervical region 

 of the cord causes acceleration, it seems evident that the path must begin 

 somewhere in the brain. It has been assumed that, like the inhibitory fibers, 

 the path starts in the medulla, and that, therefore, the cells in that organ 

 which give rise to the accelerator fibers constitute the accelerator center 

 through which reflex effects, if any, take place. As a matter of fact, the 

 location of these cells of origin has not been made out satisfactorily. The 

 matter offers unusual difficulty on the experimental side, owing to the existence 

 of the cardio-inhibitory center in the medulla and the absence of any entirely 

 satisfactory method of distinguishing certainly between reflex acceleration 

 through this center and through the accelerator center. 



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