SYMPATHETIC NERVOUS SYSTEM IN MAN 193 



which advance peripherally along the nerves which carry the 

 preganglionic fibers to each respectively, he found no evidence in 

 embryos of the rat that any of the cells which become incorpor- 

 ated in the ciliary ganglion advance peripherally along the oculo- 

 motor nerve. 



The migration of cells along the oculomotor nerve in early 

 human embryos is not very apparent; however, in a number of 

 instances an aggregate of intensely staining cells was observed on 

 the oculomotor nerve trunk at the level at which the cihary gan- 

 glion arises before cells could be traced thither from the ophthalmic 

 nerve. Doubtless, these cells become incorporated in the ciliary 

 gangUon. The ophthalmic nerve in early human embryos has 

 the appearance of a path along which active migration of cells 

 is taking place. Continuous lines of cells extend from the semi- 

 lunar ganglion along this nerve trunk. Migrant ganglion cells 

 become aggregated very early at a point just proximal to the 

 origin of the nasociliary ramus. As this aggregate of cells grows 

 larger, it advances toward the oculomotor nerve until it makes 

 intimate contact with the latter at the point at which the aggre- 

 gate of cells noted above is located. When this is accomphshed 

 the primordium of the cihary ganghon consists of a continuous 

 mass of cells extending from the ophthalmic to the oculomotor 

 nerve. This condition, as it appears in sagittal sections of an 

 embryo 14 mm. in length, is illustrated in the accompanying 

 figure (fig. 7) which is taken from the microphotograph in figure 

 21. Nerve fibers may be traced from the ophthalmic nerve into 

 the primordium of the cihary ganghon at this stage, but they are 

 largely obscured by the densely aggregated cells. As develop- 

 ment advances this ganglionic mass becomes somewhat, removed 

 from the ophthalmic nerve trunk, but remains in intimate con- 

 tact with the oculomotor nerve until relatively late. As com- 

 pared with the total number of cells comprised in the primordium 

 of the cihary ganghon in human embryos, the small group of cells 

 which becomes aggregated early on the oculomotor nerve is rela- 

 tively unimportant. Nevertheless, the evidence warrants the 

 conclusion that in human embryos, as in the embryos of other 

 vertebrates, the ciliary ganglion is genetically related both to the 

 ophthalmic and the oculomotor nerve. 



