134 



THE STUDY OF SIX AND TEN MILLIMETER PIG EMBRYOS 



lateralis into the internal jugular veins. Transverse sections may be seen of the maxillary 

 and mandibular branches of the n. trigeminus; the n. ahducens is sectioned longitudinally. Ven- 

 tral to the otocyst are seen the geniculate and acustic ganglia of the nn. facialis and acusticus. 

 The wall of the otocyst forms a sharply defined epithelial layer. More cephalad in the series 

 the endolymphatic duct lies median to the otocyst and connects with it. Dorsal to the oto- 

 cyst the n. glossopharyngcus and the jugular ganglion of the vagus are cut transversely while 

 the trunk of the n. acccssorius is cut lengthwise. 



Section through the First and Second Pharyngeal Pouches (Fig. 125).— The 

 end of the head, with sections of the telencephalon and of the ends of the olfactory pits, is now 



Fourth ventricl 



Gana.iuaulare n. 10 



GuJiQ.acust.n.d 



Mandibular ramus 

 -n.J 



/ylaxillan/ ramus 

 'n.s 



Ant lobe hypophysis 

 Lens vesicle 



Wall of 

 Myelencephalon 



M accessories 



N. glossophar- 

 yngeus 



Otocyst 



Gang, genicul. n. 7 



N. abducens 



Basilar artery 



Sinus cavern 



Int. carotid 

 artery 



Optic vesicle 



Foramen 

 interi/ent. 



Third ventricle o, 

 telencephalon 



Lat. ventricle of 

 telencephalon 



Fig. 124. — Transverse section passing through the eyes and otocysts of a 10 mm. embryo. X 22.5. 



distinct from the rest of the section. The pharynx shows portions of the first and second pharyn- 

 geal pouches. Opposite the first pouch externally is the first branchial cleft. A section of the 

 tuberculum impur of the tongue shows near the midline in the pharyngeal cavity. The neural 

 tube is sectioned dorsally at the level of Froriep's ganglion. Between the neural tube and the 

 pharynx may be seen on each side the several root fascicles of the u. hypoglossus, the fibers of 

 the nn. vagus and acccssorius and the petrosal ganglion of the n. glossopliaryngeus. Mesial to 

 the ganglia are the descending aortic and lateral to the vagus is the internal jugular vein. 



Section through the Third Pharyngeal Pouches (Fig. 126). — The tip of the head 

 is now small and shows on either side the deep olfactory pits lined with thickened olfactory epi- 



