192 



STUDY OF PIG EMBRYOS. 



original connection with the pharynx has been lost. The anlage is now isolated 

 from its parent germ-layer and is imbedded in mesenchyma. It is solid, for 



Ol.pl. 





FIG. 118. PIG. 12.0 MM. TRANSVERSE SERIES 5, SECTION 321. 







Au.4, Four i tic arch. Art. v, Vertebral artery. Au, External auditory .cleft, cl.ni, Third internal gill 



cleft. ' ~ nod, Ganglion nodosum. Hy, Hy old arch. Jug, Jugular vein, L. V, Lateral ventricle. Na, 



N.cerv.i, First cervical nerve. N.cerv.2, Second cervical nerve. A T .if, Spinal accessory 



- Hypoglossal nerve. Nv.2, Main trunk of second cervical nerve. Ol.pl, Olfactory plate. 



.0, Ramus externus of the glossopharyngeus. Sf.c, Spinal cord. T/im, Thymus. T/tyr, Thtbid. 



Tr, Trachea. X 22 diams. 



the cavities of the thyroid follicles are not develops? until considerably later. 

 Just above the third gill cleft may be seen a ' rge, d: .ained mass, 



