TIIK ANATOMY OF TKN TO TWELVE MM. PIG EMBRYOS 



119 



Tela chorioidea 

 Ncuromeres of myelencephalon 



Notochord 



Tongue 



of the pharynx are the anlages of the tongue and epiglottis (Fig. 156 A). 

 From each mandibular arch arises an elongated thickening that extends 

 caudal to the second arch. Between, and fused to these thickenings, is 

 the triangular tuberculum impar. The opening of the thyreoglossal duct 

 between the tuberculum impar and the second arch is early obliterated. 

 A .' median ridge, or copula, between the second arches connects the tuber- 



Mesencephalon 



Diencephahn 



Post, lobe of hypophysi 



Optic recess 



Tdenccphalon 

 Ant. lobe of hypophysis 



Spinal cord ~^, 



llsophagus 

 Tracltea 

 Air in in 



Dorsal Pancreas 



Hepatic divertintlitm 

 Duodenum 



L. genital fold 



L. mesonephros 



Dorsal aorta 



Colon 

 Umbilical artery (cut away) 



Metanephros 



Caecum 



mall intestine 

 'Allantois 

 Urogenital sinus 



Ureter 



Mesonephr'iC duct 



Rectum 



FIG. 122. Median sagittal dissection of a 10 mm. pig embryo, showing the brain, spinal cord 

 and viscera from the right side. X 10.5. 



culum impar with the epiglottis, which seems to develop from the bases of 

 the third and fourth branchial arches. On either side of the slit-like 

 glottis are the arytenoid folds of the larynx. (For the development of the 

 tongue, see p. 149.) The pharyngeal pouches are now larger than in the 

 6 mm. pig (Fig. 123). The first pouch persists as the auditory tube and 

 middle ear cavity, the 'closing plate' between it and the first branchial clef t 



