110 THE ANATOMY OF THE HORSE. 



The Inferior Cervical Ganglion is placed a little above the preceding, 

 to which it is connected by a shoi-t thick nerve. It rests on the longus 

 colli, between the vertebral and superior cervical arteries. It is joined 

 by the vertebral nerve, and by short branches from the inferior primary 

 divisions of the 8th cervical and first two dorsal nerves. By its posterior 

 extremity it is continued into the dorsal cord of the sympathetic. It 

 gives off a cardiac filament. 



Cardiac Nerves of the left side. — These nerves, like many others, 

 have a variable disposition, but the following is what I have found to 

 be the most common arrangement. 



The middle cervical ganglion detaches two cardiac nen^es : (1) One of 

 these (which may be double at its origin), the smaller of the two, is 

 distributed to the great arteries in the anterior mediastinum. (2) The 

 other immediately divides into two branches — a lower and an upper, 

 (a) The lower branch, joined by a filament from the vagus, passes 

 beneath the arch of the left axillary in company with the vagus, and 

 reaching the angle of bifurcation of the common aorta, it divides, one 

 branch continuing backwards on the posterior aorta to dip down 

 between the right and left divisions of the pulmonary artery and 

 gain the left auricle, while the other descends along the common 

 aorta, and uniting at the origin of the right coronary artery with 

 a cardiac branch of the right side, is distributed to the roots of the 

 great arteries and to the ventricles, the largest branches following 

 the right coronary artery. (6) The upper division of the second nerve, 

 passing to the inner side of the left axillary, and along the lower face 

 of the trachea, unites with a right cardiac filament, crosses to the 

 right of the common aorta, and is reflected round that trunk to gain 

 the left coronary artery, its divisions following the main branches of 

 that vessel. 



The inferior cervical ganglion detaches a slender cardiac nerve which, 

 after throwing off some twigs to the aileries in the anterior medias- 

 tinum, passes downwards and backwards to the left auricle. 



[" The cardiac nerves of the horse (left side) ordinarily have the following disposition : 

 There are found four nerves, two of which, very slender, jjroceed from the middle 

 cervical ganglion and lose themselves on the vessels arising from the convexity of the 

 brachial trunk. The two others are the one superficial, the other deep. The superficial 

 nerve, the more voluminous, commences by a filament which springs from the middle 

 cervical ganglion, passes backward and downwards, contracts beneath the brachial trunk 

 an anastomosis en arcade witli a branch detached from tlie inferior cervical ganglion, and 

 then places itself alongside of the following. The deep nerve is formed at first by three 

 elements : (1) of medullary fibres furnished by the spinal pairs ; (2) of a ramuscule 

 furnished by the cervical cord of the sympathetic ; (3) of a slender filament which pro- 

 ceeds from the left pneumogastric at the entrance to the chest. It places itself in the 

 direction of the heart, adheres to the superficial nerve, is inflected on tlie concavity of 

 the brachial artery, margins this vessel to the left and insinuates itself between the aorta 

 and the pulmonary artery. At this point these nerves are distributed to the heart and to 

 the great vessels, a branch passes iinder the right auricle and plunges into the cardiac 



