MAMMALIA. 173 



across the spine behind the oesophagus, and communicate with some from a similar 

 plexus on the left side, whilst others pass behind the inferior vena cava, and give 

 branches to the left auricle and ventricle, and near the azygos vein become connected 

 with the left thoracic plexus, which also gives branches to the left auricle and 

 ventricle. 



In simise, the jaguar, dog, fox, hedgehog, and rabbit, the prolongation is a thick 

 and narrow cord similar to that in man, but in herbivorous animals, as the ass, calf, 

 and goat, it is broad and flat, and composed of parallel threads communicating with 

 each other ; in the pig, its disposition is more close, but it is broader and less compact 

 than in the dog, jaguar, and others, and contains similar close and fleshy ganglia ; in 

 the calf, small ganglia are imbedded in it, which in the ass rather form an areolar 

 disposition of some of the threads ; near the bottom of the chest, however, two or 

 three small fleshy ganglia are observed ; on the inner side, these ganglionic spots give 

 filaments to the aorta, and, on the outer, communicate with each intercostal nerve; 

 in the ass, it continues of almost the same breadth nearly throughout the thorax, but 

 above the last rib but four begins to separate from the splanchnic nerve, to which, 

 however, it adds fresh branches ; in the calf, after the thoracic plexus is given off, it 

 becomes narrower; it then, in descending, gradually gets broader after its commu- 

 nication with each intercostal nerve, and appears rather to have had a branch added 

 to it by, than to have given one to, each intercostal nerve. Although the splanchnic 

 nerve adheres so closely to the prolongation, it may, by a careful dissection, be 

 separated from this, and resolved into the several cords of origin very similar to 

 those in man, but not without dividing connecting filaments. It passes through the 

 diaphragm to the semilunar ganglion, and forms a close union with the renal capsule, 

 and then sends off the prolongation. The thoracic portion differs in several animals 

 as to its manner of giving off the splanchnic nerves. In the baboon and hedgehog, 

 but not in the monkey, the splanchnic nerve forms a plexus on the sides of the bodies 

 of the vertebrae, which is very similar to that in man ; and in the baboon the right 

 arises from two ganglia higher than the left, and extends over the heads of seven 

 inferior ribs, the left over only five ; each expands into a small ganglion at the bottom 



