APPENDAGES OF THE NERVES. 323 



of the nerve ; subsequently two dorsal ganglia occur, and further 

 down, towards the middle of the back, there occurs a third and last 

 ganglion, which furnishes the splanchnic nerve : the remainder of 

 the sympathetic is made up of one or two cords, which, in the 

 sacral region, give off a great number of branches, the divisions of 



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which form the renal, hypogastric, and sacral plexuses. 



In the Turtle ( Chelone) the cervical portion of the sympathetic 

 has the same exposed position, and communications, with the vagus 

 above and the axillary plexus below, sending off filaments also to 

 the arteries. The branch accompanying a division of the carotid 

 in a canal at the base of the skull gives a filament to the portio 

 dura, and communicates with the maxillary part of the fifth, to 

 terminate on the back part of the palate. Another branch enters 

 with another division of the carotid into the reticular sinus close 

 to the auditory meatus, and communicates with the portio dura, 

 glossopharyngeal, and ninth nerves. In the trunk-cavity, the 

 sympathetic passes from ganglion to ganglion as two cords, a thick 

 and a fine one, neither of which passes behind the neck of the 

 rib ; the intercommunicating branches with the spinal nerves are 

 perforated by an anterior branch of the intercostal artery. The 

 chief nerves given off from the sympathetic form two plexuses, in 

 the place of the ( semilunar ganglia ' of mammals : the smaller 

 plexus sends filaments along the coeliac artery to the stomach, the 

 larger plexus along the mesenteric artery to the intestines. Other 

 branches pass to the kidneys, and the communications with the 

 spinal nerves mark out the delicate prolongation of the sympa- 

 thetic to behind the rectum. 



In the Crocodile the cervical part of the sympathetic lies in 

 the ( vertebral canal,' or between the neck and tubercle of the rib, 

 and the ganglions are more distinct where the communications 

 with the spinal nerves occur, from the cervical to the lumbar 

 region. The interganglionic longitudinal trunks are two, one 

 passing behind the neck of the rib where it exists, at the fore-part 

 of the chest. The longitudinal trunks converge, and unite upon 

 the beginning of the caudal artery. There is much pigmental 

 matter upon the sheaths of the ganglions and nerves. 



60. Appendages of the Nervous System. - - Certain nerves, as 

 those of the palm and sole in Man, and those of the mesentery in 

 other mammals, have peculiar corpuscles appended to them, called 

 'pacinian,' after their discoverer. Fig. 213 shows one of the nerves 

 of the palm with the corpuscles appended, of the natural size. 

 Those in the mesentery of the cat are numerous, conspicuous, and 

 favourable subjects for microscopical investigation. They show 



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