CARDIAC PLEXUS. 373 



The left or anterior coronary plexus is larger than the right, and is derived 

 mainly from the left half of the deep cardiac plexus. Being directed forwards 

 between the pulmonary artery and the left auricular appendage, it reaches the left 

 coronary artery, and subdivides into two principal portions which accompany the 

 primary divisions of that vessel. 



Nervous filaments ramify in great number under the epicardium, especially on the 

 ventricular portion of the heart. They are not so easily distinguished in man as in 

 some animals. In the heart of the calf or the lamb they are distinctly seen without 

 dissection, running in lines which cross obliquely the muscular fibres. Microscopic 

 ganglia occur on the nerves of the auricles, and in the course of the coronary 

 plexuses, but they are absent from the offsets to the ventricular wall (see Vol. II, 



Fig. 236. DIAGRAMMATIC REPRESENTATION OP THE CARDIAC PLEXUS OP THE HUMAN EMBRYO. 



(W. His, jun. ) 



a, aorta ; a', pulmonary artery ; b, atrium, with the orifices of the veins ; Au, auricle proper ; 

 v, ventricle ; vg, vagus ; sy, cord of sympathetic ; p, p, pericardium ; s, transverse sinus of peri- 

 cardium ; I, bulbar plexus ; II, atrial plexus ; III, intermediate plexus. 



From the embryological investigations of W. His, jun., it appears that the ascending aorta, 

 the pulmonary trunk, and the ventricles of the heart are supplied by the upper cardiac nerves, 

 while the auricles receive branches arising- at a lower level. The earliest of the cardiac nerves 

 to be developed are branches from both vagus and sympathetic of each side to the arterial 

 bulb, which appear about the end of the fourth or the beginning of the fifth week of foetal 

 life, and make their way between the aorta and the pulmonary trunk, where they form the 

 bulbar plexus. In the seventh week other nerves are found passing from the vagi lower down 

 to the back of the auricles, and forming there the atrial plexus, which also receives 

 sympathetic branches through the following plexus. The bulbar anel atrial plexuses are 

 connected by branches which descend from the former behind the transverse sinus of the peri- 

 cardium, and are joined by offsets of both vagi, the left recurrent nerve, and the sympathetic 

 cords, the whole constituting the intermediate plexus. All of these branches contain numerous 

 ganglion-cells of sympathetic nature, which travel downwards with the growth of the nerves. 

 In the course of the third month the coronary nerves are developed from the bulbar plexus, 

 and offsets of the atrial plexus spread over the auricles. In the definitive state therefore the 

 bulbar plexus is represented by the superficial cardiac plexus and a part of the deep cardiac 

 plexus, with their coronary offsets, the intermediate plexus by the remainder of the deep 

 cardiac plexus, and the atrial plexus by the network on the auricles. The distribution of 

 the ganglia in the adult heart corresponds to the extent of these plexuses. 



SOLAR OR EPIGASTRIC PLEXUS. 



The solar or epigastric plexus (plexus cxliacus), the largest of the prevertebral 

 centres, is placed at the upper part of the abdomen, behind the stomach, and in 



