94 



THE STUDY OF SIX AND TEN MILLIMETER PIG EMBRYOS 



two sides. Posterior to this groove and extending in the median Kne to the 

 hyoid arch is a triangular rounded elevation, the tuherculum impar, which later 

 forms a small part of the tongue. At an earlier stage the median thyreoid anlage 

 grows out from the mid- ventral wall of the pharynx just caudal to the tuherculum 

 impar. The ventral ends of the second arch fuse in the mid-ventral hne and 

 form a prominence, the copula. This connects the tuherculum impar with a 



Pharynx 



Neuromere 4 Rathke's pocket 



Anlage of 

 tongue 



R. air 



Esophagus 



Interatrial 



foramen 



Lung bud 



L. genital fold 



Isthmus 



Mesencephalon 

 Diencephalon 



Bulbus cordis 

 Telencephalon 

 Ventricle 



Septum irans- 

 versum 



Liver 



Yolk sac 



Allantois 



Tail gut 



Cloaca 



Metanephros 



Spina] rurd 



Caudal limh of intestine 

 Mesonephric duct 



R. mesonephros 

 Fig. 96.— Median sagittal dissection of a pig embryo of 6 mm,, to show viscera and neural tube. X 18. 



rounded tubercle derived from the third and fourth pairs of arches, the anlage 

 of the epiglottis. Its cephalic portion forms the root of the tongue (Fig. 156). 

 Caudal to the epiglottis are the arytenoid ridges, and a sht between them, the 

 glottis, leads into the trachea. 



The branchial arches converge caudad and the pharynx narrows rapidly 

 before it is differentiated into the trachea and esophagus (Figs. 104 and 105). 



