596 



HEART. 



The left middle cardiac nerve is generally 

 smaller than the right, and is frequently partly 

 formed by a branch from the inferior cervical 

 ganglion. It passes behind the arch of the 

 aorta, sometimes in the form of a single trunk, 

 sometimes double, at other times triple, and 

 generally throws itself into the upper and left 

 part of the cardiac plexus. 



Cardiac plexus (great cardiac plexus of 

 Haller) is placed behind the arch of the aorta 

 and in front of the lower part of the trachea, 

 extending from the arteria innominata to the 

 right branch of the pulmonary artery, and is 

 formed by the convergence of nearly the whole 

 of the cardiac nerves of both sides, but more 

 particularly of the middle cardiac nerves. 

 There is occasionally a distinct ganglion at the 

 junction of these nerves; more generally there 

 is only a plexiform arrangement. From this 

 plexus a very few branches pass upon the ante- 

 rior surface of the aorta (curdiaci superficiales 

 aorta), and anastomose with the right coronary 

 plexus : some twigs also pass backwards to 

 anastomose with the bronchial plexuses. By 

 far the greater part of the cardiac plexus pro- 

 ceeds to the heart in the form of two large 

 divisions to form the right and left coronary 

 plexuses which accompany the coronary arte- 

 ries. Where the right branch leaves the lower 

 part of the plexus there is a gangliform swelling 

 (ganglion of Wrisberg), which is occasionally, 

 however, very indistinct. This ganglion fur- 

 nishes the greater part of the superficial plexus 

 of the aorta which we have just described. This 

 great right cardiac branch divides into two 

 parts ; the smaller passes between the aorta and 

 pulmonary artery to reach the right side of the 

 origin of the pulmonary artery, where it attaches 

 itself to the right coronary arteiy to form the 

 principal part of the right coronary plexus ; the 

 other and larger portion creeps under the pul- 

 monary artery to the posterior part of the heart, 

 to assist in forming the left coronary plexus. 

 The great left cardiac branch, which principally 

 comes from the upper part of the cardiac plexus, 

 and at first passes from right to left posterior to 

 the ductus arteriosus, after which it is joined 

 by other smaller branches which pass in front 

 of the ductus arteriosus. It also divides into 

 two branches ; the smaller passes between the 

 aorta and pulmonary artery, and reaches the 

 origin of the right coronary artery, and throws 

 itself into the right coronary plexus ; the larger 

 bends round the posterior surface of the pulmo- 

 nary artery to reach the left coronary artery, 

 where it forms, with the larger branch of the 

 right, the left coronary plexus. There is thus 

 a free interchange of filaments between the 

 nerves of both sides. The left coronary plexus 

 is considerably larger than the right, in propor- 

 tion as the left side of the heart is thicker than 

 the right. These coronary plexuses consist of 

 a number of minute filaments which accom- 

 pany the ramifications of the coronary arteries 

 everywhere, and are distributed upon the sur- 

 face of the auricles as well as upon the ventri- 

 cles, They anastomose with each other upon 

 the anterior and posterior surface of the heart. 

 All the nerves of the heart enter into its sub- 



stance upon the surface of the arteries, and 

 cannot be traced beyond the second or third 

 division of the arteries. The nerves of the 

 heart are generally considered to be small com- 

 pared to the size of the organ.* Though the 

 nerves of the heart are not equal in size to 

 those of the tongue and eye, yet Scarpa is 

 doubtful if they are not equal to the nerves of 

 the other voluntary muscles, as, for example, 

 the muscles of the arm. It must be remem- 

 bered that the minute subdivision and diffusion 

 of these nerves over a large extent of surface, 

 by which many of them can only be seen after 

 a minute examination, causes them to appear of 

 less size than what they collectively really are. 

 Soemmerring maintained that very few of the 

 nerves of the heart were distributed to the mus- 

 cular tissue of the heart, and that they more 

 properly belonged to the arteries : " nervi car- 

 diaci proprie ad arterias, ad aortam et arterias 

 coronarias pertinent, eaque filia subtilia nervo- 

 rum parum sibi (cordi) constant." f Behrends, 

 the pupil o| Soemmerring, affirmed that not a 

 single twig went to the muscular tissue of the 

 heart, but that they were entirely distributed on 

 the coats of the arteries.]; The announcement 

 of these opinions, bearing so directly as they do 

 upon the Hallerian doctrine of the nature of 

 irritability, so keenly agitated immediately be- 

 fore throughout Europe, could not fail to create 

 considerable sensation at the time, and it is 

 probable that to this we owe the splendid work 

 of Scarpa upon the nerves of the heart, which 

 has entirely set the question concerning the dis- 

 tribution of these nerves at rest. Scarpa has 

 shown that when followed to their minute dis- 

 tribution, the nerves of the other muscles ac- 

 company the arteries in the same manner as 

 the nerves of the heart, and that the nerves of 

 the heart only differ from those of voluntary 

 motion in this, that the nerves accompanying 

 the arteries of the voluntary muscles are firmer 

 and thicker than those of the heart. 



Bloodvessels of the heart. The heart is sup- 

 plied with blood by the two coronary arteries, 

 for a description of which see AORTA. The 

 blood is returned by the coronary veins. The 

 branches of the coronary veins generally accom- 

 pany those of the arteries. They are divided 

 into the larger coronary vein and smaller coro- 

 nary veins. 



Great coronary vein (vena coronaria maxima 

 cordis). This vein is formed by several 

 branches, three of which surpass the others 

 considerably in size. One of these lies in the 

 anterior louoitudinal groove ; another runs along 

 the obtuse or left margin of the heart ; and the 

 third, which may be replaced by two or three 



* Bichat in his Anatomie Generale says, " that 

 the nervous mass intended for the muscles of orga- 

 nic life is much inferior to that of the voluntary 

 muscles. The heart and deltoid muscle, on being 

 compared together, display in this respect a very 

 considerable difference." 



t Corporis humani fabrica, torn. v. 



J Dissertatio qua demonstratur cor nervis carere. 

 After making this general statement, he admits, in 

 one part of his treatise, that he has traced two 

 twigs of the cardiac nerves into the substance of the 

 heart. 



