238 CIRCULATION OF THE BLOOD. 



column (lone/us colli), and consequently to the inner side of 

 the tendinous origins of the scalenus anticus from the trans- 

 verse processes. It has the oesophagus on its inner side, the 

 vertebral artery on its outer, and lies behind the carotid artery 

 and internal jugular vein. The following are the best guides 

 to its discovery: Superficially, the junction of the external 

 jugular vein and subclavian vein to form the vena innominata, 

 in the angle between which vessels the phrenic nerve appears 

 lying on the scalenus anticus ; more deeply, the origins of the 

 scalenus anticus, from the two last cervical transverse pro- 

 cesses ; and particularly the vertebral artery where it passes 

 to the inside of these insertions, to enter the foramen trans- 

 versarium of the sixth cervical vertebra. The upper end of 

 the ganglion is to be found close to the artery on its inner 

 side. The ganglion receives from above, in addition to the 

 sympathetic trunk, communicating branches from the brachial 

 plexus and from the vagus, and a branch (the so-called radix 

 brevis) whicli accompanies the vertebral artery. Downwards, 

 the ganglion sends (besides those leading to the first thoracic 

 ganglion) branches which go towards the heart. One of the 

 most internal of these is the continuation of the depressor 

 nerve, to be hereafter mentioned, which rather passes by the 

 ganglion than springs out of it, and looses itself in the plexus 

 of nerves between the aorta and pulmonary artery. The com- 

 munication between the lower cervical and the first thoracic 

 ganglion takes place by two nerves, one of which passes in 

 front of, the other behind, the subclavian artery, before that 

 artery gives off the vertebral. The accelerator fibres enter 

 the ganglion by the vertebral nerve, and thence find their way 

 to the heart through the cardiac plexus already mentioned. 

 (See explanation of fig. 241.) 



In the dog, the arrangement of the accelerator nerves is 

 somewhat different. In this animal, as in the rabbit, the 

 lower cervical ganglion lies on the longus colli immediately to 

 the inner side of the vertebral artery, and above the subclavian. 

 It is connected with the first thoracic ganglion by two twigs, 

 one of which passes behind the subclavian and vertebral arte- 

 ries, the other in front of them. Of its cardiac branches, of 

 which three have been distinguished by Cyon, the most im- 

 portant accompanies the recurrent nerve until that nerve 

 bends upwards to its distribution, and then follows the sub- 

 clavian or innominate artery to gain the cardiac plexus. From 

 above, the ganglion receives, first, the combined trunk of the 

 vagus and sympathetic, which here separate from each other, 

 the former continuing its course into the thorax ; and secondly, 

 two branches corresponding to those described in the rabbit. 

 The accelerator fibres are very variously distributed among 

 these several branches, sometimes finding their way to the 



