SYMPATHETIC NERVOUS SYSTEM IN , MAN 211 



common both along the paths of migration and in the primordia of 

 the sympathetic gangha. Therefore, we must conclude that 

 many of the elements which become differentiated into sympa- 

 thetic neurones arise bj^ the mitotic division of migrant cells 

 either before or after they have become incorporated in the pri- 

 mordia of the sympathetic nervous system. According to this 

 interpretation, the sympathetic system is entirely homologous 

 with the other functional divisions of the nervous system. 



SUMMARY 



The primordia of the sympathetic trunks and the prevertebral 

 plexuses arise from cells of cerebrospinal origin which advance 

 peripherally both along the dorsal and ventral roots of the spinal 

 nerves. 



The vagal sympathetic plexuses, viz., the pulmonarj^, the car- 

 diac, and the enteric plexuses, except in the aboral portions of 

 the digestive tube, arise from cells of cerebrospinal origin which 

 advance peripherally along the vagi. In the more distal portions 

 of the digestive tube the enteric plexuses arise from cells which 

 are derived from the sympathetic supply in the lower trunk region. 



The majority of the cells which constitute the primordium of 

 the ciliary ganglion are derived from the semilunar ganglion via 

 the ophthalmic nerve. Relatively few cells are contributed via 

 the oculomotor nerve. 



The cells which enter the primordium of the sphenopalatine 

 ganglion earliest advance peripherally along the greater superficial 

 petrosal nerve. The majority of the cells which enter the pri- 

 mordium of this ganglion are derived from the semilunar ganglion 

 via the maxillary nerve and its rami. 



The primordium of the otic ganghon arises at the growing 

 extremity of. the lesser superficial petrosal nerve as an aggregate 

 of cells which advance primarily from the petrosal ganglion. 

 The otic ganglion also receives cells of trigeminal origin via the 

 mandibular nerve and its rami. 



The submaxillary and sublingual ganglia arise on the lingual 

 nerve primarily from cells of trigeminal origin. They probably 

 receive some cells of facial origin via the chorda tympani. 



