TRANSVERSE SECTIONS OF EMBRYO OF 12 MM. 



269 



sections next following the complicated pharynx appears in various forms. The 

 general shape of the pharynx has been described with the aid of a figure of a wax 

 model of the pharynx made from the same series of sections from which these 



D.Z 



V.Z 



L.R.II. 



N.I 2. 



L.V. 



II 



EC. 





_ FIG. 192. PIG, 12.0 MM. TRANSVERSE SERIES 5, SECTION 249. 



Card, Anterior cardinal vein. Car.in, Internal carotid artery. cl.I, First or auditory gill-cleft. D.Z, Dorsal zone 

 of spinal cord. EC, Ectoderm. H, Anlage of cerebral hemisphere. L, Lens. L~K.II, Lateral rooi of th- 

 iith nerve. L.V, Lateral ventricle. Mx.in, inferior maxillary nerve. NJ\ Facial nerve. X.y.petr* 

 1'etrosal ganglion of the ninth nerve. A7".io,iT, United vagus and spinal acdpsory nerve. A'. 12, Hypo-i 

 glossal nerve. Op, Stalk of the optic ^vaginal ion. Op.v, Ophthalmic vein.fPh, Pharynx. Ret. Rttina. 

 , .^, Ventral zone of spinal cord. X 22 chams. 



figures are taken (compare Fig. 173, p. 237). The shaperbi the pharynx and of 

 its four pairs of latei ^ ..ches at this stage is remarkably' constant, so tha* the s* 

 dent is not likely to encounter any serious difficulty in /dentif)] 

 spinal co-,-tl is oval in the section. Its cavity has expinded in thi 



