PLATE 4 



EXPLANATION OF FIGURES 



21 Human embryo, 14 mm. in length, 511 — ^12 — 2 — 2X160. Sagittal section 

 through primordium of ciliary ganglion (eg). OCN, oculomotor nerve; Op, oph- 

 thalmic nerve. 



22 Human embryo, 13 mm. in length, 485 — S — 2 — 2X335. Section showing 

 apparent cellular continuity between semilunar and otic ganglia. Man, mandib- 

 ular nerve; og, otic ganglion; SG, semilunar ganglion. 



23 Human embryo, 14.6 mm. in length, 1919 — 11 — 2 — 2X160. Coronal sec- 

 tion showing maxillary ramus (mr) leading into primordium of sphenopalatine 

 ganglion (xpg). gfip, nerve of the pterj'goid canal which includes the fibers of 

 the greater superficial petrosal nerve ;M. maxillary nerve ;»SG', semilunar ganglion. 



222 



