THE ANATOMY OF TEN TO TWELVE MM. PIG EMBRYOS 



119 



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- 



Metencephalon 

 Tela chonoidea 



Mesencephalon 



Neuromeres of myelencephalon 



Nolochord 

 Tongue 



Spinal 



Esophagus 

 Trachea 

 Atrium 



Dorsal Pancr 



Diencephalon 



Post, lobe of hypophysis 



Optic recess 



Telencephalon 

 Ant. lobe of hypophysis 



Bulbus corals 

 Ventricle 

 Yolk sac 



Septum transversum 

 Yolk stalk 

 Liver 



Hepatic diverticulum 

 Duodenum 



L. genital fold 



L. mesonephros 



Dorsal aorta 



Colon 



" Caecum 



Small intestine 

 "Attantois 

 Vrogenital sinus 



'Ureter 



Mesonephric duct 

 Umbilical artery (cut away) 



Metanephros 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 



