THE NERVOUS REGULATION OF THE HEART 165 



in accordance with its greater mass the left ventricle receives more 

 fibres than the right. 



Stimulation of the accelerator nerves in the dog causes an 

 increase in the force of both the auricular and ventricular con- 

 traction, and as a rule, in addition, some increase in the rate of 

 the beat. 



As to the nature of the physiological linkage between the cardiac 

 nerves and the muscular tissue of the heart we know but little. 

 Ganglion-cells lie on the course of the vagus fibres after they 

 have entered the heart, and although the view has been advocated 

 that they are simply stations where the inhibitory impulses pass 

 from medullated to non-medullated fibre s, and where possibly other 



Fig. 75- L ood-Pres-u 2 Tracings: Rabbit. Vagus stimulated at i. Stimulus 

 siruuger in B than in A (Hiirthle's spring manometer). 



anatomical changes and rearrangements occur, they may be inter- 

 mediate mechanisms which essentially modify the physiological 

 impulses falling into them. It has been stated that in the dog the 

 right vagus controls chiefly the rate of the heart, and the left vagus 

 chiefly the conduction from auricles to ventricles, and the suggestion 

 has been made that this is because the right vagus has a special 

 relation to the sino-auricular node, in which impulses are supposed 

 to arise, and the left vagus a special relation to the auriculo-ven- 

 tricular node, the upper end of the A-V bundle, the main conduction 

 system (Cohn and Lewis). 

 The nervi accelerantes are already non-medullated before they 



