TRANSVERSE SECTIONS OF A TEN MM. PIG EMBRYO 



127 



and mandibular branches of the n. trigeminus; the n. abducens is sectioned longitudinally. 

 The small nn. oculomotorius and irochlearis should be identified in sections more cephalad in 

 the series. Ventral to the otocyst are seen the geniculate and acoustic ganglia of the nn. facialis 

 and acusticus. The wall of the otocyst forms a sharply defined epithelial layer. More cephalad 

 in the series the endolymph duct lies median to the otocyst and connects with it. Dorsal to 

 the otocyst the n. glossopharyngeus and the jugular ganglion of the vagus are cut transversely 

 while the trunk of the n. accessorius is cut lengthwise. 



Section through the First and Second Pharyngeal Pouches (Fig. 130). — The 

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



N. accessoiius 



Gang. Front p 



Myeknceph ilon 



Basilar artery 



Notochord 



^ II al cavity 



Gang, petrosal n. g 

 Pharyngeal pouch 2 



Pharyngeal pouch i 



Oral cavity A 



Olfactory pit 



Roots of n. hypoglossus 



Int. jugular vein 



Nn. vagus et accessorius 

 Descending aorta 



N. facialis 

 Branchial arch 2 

 Tongue 

 Ulandible 



Maxillary process 



Telencephalon 



Fig. 130. — Transverse section passing through the first and second pharyngeal pouches of a 10 mm. pig 



embryo. X 22.5. 



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

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

 of the tuberculum impar 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 n. hypoglossus, the 

 fibers of the nn. vagus and accessorius, and the petrosal ganglion of the n. glossopharyngeus. 

 Mesial to the ganglia are the descending aortce and lateral to the vagus is the internal jugular 



