304 



TEXT-BOOK OF PHYSIOLOGY. 



heart just beneath the pericardium. From the cell-body fine non-medullated 

 fibers pass into the substance of the heart, to become histologically and 

 physiologically related with the muscle-fiber. 



In the dog heart and in the mammalian heart generally, though nerve- 

 cells are present, they are not arranged in such definite groups, but are more 



Emotion a I Cen ters 



Exhilarating (BLUE) 

 *eo) 



Cantio -Inhibitor Center. 



Ganglion Stellatum 



Intra-Carctiactferoe Cells 



Canfio -Accelerator Center 



erve 



tutor (BLUI.} 

 bitor (BLUE) 



ffenntInhibltor(RED) 



Sympath etic Mroes ' 



Accelerator & Auymen tor 



FIG. 140. DIAGRAM OF THE NERVE MECHANISM OF THE HEART. (G*. Bachnnm.} 



widely distributed in the terminations of the venae cavae, pulmonary veins, 

 the walls of the auricles, and in the neighborhood of the base of the ventricles. 

 - Extra-cardiac Nerves. The extra-cardiac nerves which connect the 

 heart with the central nerve system and through which the activities of the 

 heart are influenced are two: viz., the sympathetic and the vagus or pneumo- 



