2$& Nerves of tie Vijccra. [Book IX. 



unite to form a third ganglion. After this the trunk 

 of the intercoftal pafles down by the fpine, clofe to 

 the tranfverfe procefTes, through the cavity of the 

 thorax. In this courfe all the dorfal nerves as they 

 come from the fpine contribute to its increafe by the 

 addition of twigs on each fide. Defcending ftill lower 

 it receives fimilar accefilons from the nerves which 

 come out between the lumbar vertebras and os facrum. 

 At the extremity of the os coccygis the intercoftals 

 of the oppofite fides are turned inwards, and unite 

 with each other. The intercoftal is larger in the 

 thorax than it is either above or below. 



From the part whence the fifth, fixth, leventh, 

 eighth and ninth dorfal nerves are fent to the inter- 

 coftal, come out as many branches, which form an 

 anterior trunk called the fmall intercoftal nerve. This 

 pafles through the pofterior part of the diaphragm to 

 form, with the grearintercoftal of the oppofite fide, and 

 with the eighth pair, a large femi-lunar ganglion, 

 fituated between the cseliac and fuperior mefenteric 

 arteries. From this ganglion, as from a center, nerves 

 are fent to the liver, pancreas, fpleen, duodenum, 

 jejunum, ileum, and a large part of the colon. 



Several fibres alfo palling downwards on the aorta, 

 are joined by other nerves from the pofterior trunk of 

 the intercoftal, and form plextifes, which fupply the 

 kidneys, glandulas fuprarenales, &c. They alfo form 

 a plexus about the inferior mefenteric artery, which 

 accompanies its branches to that part of the colon 

 which lies at the left fide of the abdomen, and to the 

 reclum. 



The firft cervical pair of nerves comes out between 

 the firft and fecond cervical vertebras; the fecond cer- 

 vical pair between the fecond and third. Thefe nerves 

 communicate with each other, and with thofe nerves 



of 



