184 ANATOMY OF VERTEBRATES. 



spreading over its cellular part g, most of them passing either 

 forward at b, or backward at a, and thus adding to the substance 

 of the main trunk, A, B. 



These ganglionic enlargements are more distinct from, and 

 proportionally larger than, the cords in Man and Unguiculates, 

 than in Ungulates and some lower Mammals. There is also some 

 difference in the character of the cords themselves. In the 

 Quadrumana and Carnivora, dissected by Swan, as well as in 

 the hedgehog and rabbit, the cord was ' thick and narrow ' as 

 in Man : but in the ass, calf, and goat it was broad and flat, 

 and composed of parallel threads communicating with each other. 

 In the ass it continues of almost the same breadth nearly through- 

 out the thorax. ' In the calf, after the thoracic plexus is given 

 off, it becomes narrower ; it then, in descending, gradually gets 

 broader after its communication with each intercostal nerve, and 

 appears rather to have had a branch added to it by, than to have 

 given one to, each nerve.' 1 The thoracic portion of the sympa- 

 thetic supplies nearly the same parts as in Man. In the jaguar, 

 branches from several of the thoracic ganglia of the right side 

 unite and communicate with the right posterior pulmonary plexus, 

 and then cross the spine to communicate with the left posterior 

 pulmonary plexus. In the calf, a similar plexus gives off the 

 more inferior cardiac nerves to the left auricle and ventricle : it 

 proceeds from four or five of the thoracic ganglia of the right 

 side, and communicates with the vagal nerve: branches extend 

 across the spine behind the gullet, and communicate with some 

 from a similar plexus on the left side. The first or anterior 

 thoracic ganglion is commonly notable for its size, and sends off 

 filaments of communication with the vagal, recurrent, and phrenic 

 nerves. The cord between the first thoracic and last cervical 

 ganglion is short, and usually divided, or traversed, by the 'sub- 

 clavian ' or 6 trunk of the brachial ' artery. In Man the two 

 ganglions seem to blend into one. The lower cervical is always 

 a notable ganglion : the inferior cardiac nerves proceed from it. 

 The sympathetic trunk divides and passes forward along the neck : 

 the smaller portion, along the vertebrarterial canal, answers to 

 the cervical part of the trunk in birds : the larger portion extends 

 in close connection with the trunk of the vagus, and ' in the 

 calf it has sometimes very small ganglia' imbedded in it, 

 which give filaments to accompany the small arteries.' 2 In the 

 hedgehog and rabbit this connection between the sympathetic 

 and vagus is less intimate. In this part of the sympathetic there 

 1 liv. p. 115. 2 lb. p. 113. 



