COURSE OF POSTGANGLIONIC FIBRES. 



623 



ophthalmic branch of the fifth nerve, and that stimulation of this 

 nerve — normally producing dilatation of the pupil — no longer had an 

 effect. 



That the degeneration, after section of the internal carotid branches, 

 spreads to the periphery, is shown by stimulating the sclerotic before 

 and after the degenerative section. In the former case, there is a double 

 effect — local contraction of the radial muscle leading to local enlarge- 

 ment of the pupil, and local contraction of the circular muscle of the 

 iris ; in the latter case, the radial contraction is lacking, the circular 

 takes place as before. 



General plan of arrangement.— The general idea of the sympathetic 

 supply to the head, which we gather from the foregoing, is as follows : 

 — The upper part of the thoracic spinal cord sends out fibres by the 

 anterior roots of the spinal nerves of this region. The fibres make no 

 halt at the ganglia until they reach the superior cervical ganglion. 

 This is a relay station for the sympathetic nerve supply of the whole of 

 the head ; in it all the nerve fibres form nerve-endings — synapses as 

 they are called by Foster ; probably, indeed, as we shall see later, 

 each nerve fibre branches and so forms several nerve-endings, each 

 in connection with a nerve cell. Each nerve cell sends off a nerve 

 fibre, which runs to the periphery, where it branches and supplies 

 a group of unstriated muscle or gland cells. On the course of a 

 nervous impulse from the spinal cord to the periphery, there are, then, 

 two nerve cells, one with cell body in the spinal cord, the other with 

 cell body in the local sympathetic ganglion. The nerve fibre of the first 

 nerve cell we may call a pre-ganglionic fibre, that of the second a post- 

 ganglionic fibre. 



In introducing the terms pre-ganglionic and post-ganglionic, 1 I mentioned 

 also the terms pre-cellular and post-cellular. I rejected the latter, since they 

 are less distinctive. A pre-ganglionic fibre is post-cellular in relation to the 

 nerve cell from which it arises. Kolliker,' 2 however, prefers to use either 

 pre-cellular and post-cellular, or " Motorische Eingeweide-Fasern, I. und II. 

 Ordnung." 



Course of post-ganglionic fibres.— A further point that concerns 

 us is the course taken by the post-ganglionic fibres of the superior 

 cervical ganglion on their way to the periphery. Our information with 

 regard to this is not very full or well assured. The majority of the 

 fibres which have been traced, pass to the fifth cranial nerve, and are 

 distributed with its sensory fibres. 3 Thus the pupillo-dilator fibres and 

 other fibres to the eye pass to the ophthalmic branch of the fifth, and the 

 long ciliary nerves ; the fibres — whether constrictor or dilator — to the 

 blood vessels of the lips and mucous membrane of the mouth and nose, 

 pass by the superior and inferior maxillary branch of the fifth. Broadly 



1 Journ. Physiol., Cambridge and London, 1893, vol. xv. p. 178. 



2 "Handbnch d. Gewebelehre," Bd. ii. S. 855. 



3 Waller and Budge, Corrupt, rend. Acad. d. se., Paris, 1851, tome xxxiii. p. 418 (pupillo- 

 dilator fibres); Wegner, Arch. f. Ophth., Leipzig, 1866, Bd. xii. S. 16 (vasoconstrictor 

 fibres to iris) ; Francois-Franek, Trav. de Lab. de Marey, 1880. (According to Francois- 

 Franck, the vaso-constrictor fibres to the iris run in the internal carotid plexus and not in 

 the cervieo-Gasserian strand.) Jegorow, Arch. f. Physiol., Leipzig, 1886, S. 149 ; Luch- 

 singer, Hermann's "Handbnch," 1883, Bd. v. Th. 1, S. 421 et scq. (sweat fibres) ; Dastre 

 and Morat, "Systeme vaso-moteur," Paris, 1884, p. 116 (vaso-dilator) ; Morat, Arch, de 

 physiol. norm, etjpath., Paris, 1889, p. 196. I have found that the pilo-motor nerves for 

 the face area accompany the fifth nerve. 



