ISO 



THE DISSECTION OF PIG EMBRYOS 



The tongue develops as two distinct portions, the body and the root, separated 

 from each other by a V-shaped groove, the sulcus terminalis. In both human 



and pig embryos the body of the tongue is 

 developed from three anlages which are 

 formed in front of the second branchial 

 arches. These are the median, somewhat 

 triangular tuberculum impar, and the paired 

 lateral swellings of the first, or mandibular, 

 arches, both of which are present in human 

 embryos of 5 mm. (Figs. 98 and 157 A). 

 At this stage, a median ventral elevation 

 formed by the union of the second branchial 

 arches (and, according to some workers, the 

 This, with the portions of the second arches 



Between it and the 



Fig. 155. — Lateral view of the head 

 of a 7 mm. pig embryo. The three 

 lines indicate the planes of sections to be 

 made in dissecting the tongue as de- 

 scribed in the text. 



third as well) forms the copula. 



lateral to it, forms later the base or root of the tongue 



Branchial arch i 

 Tuberculum impar 



Branchial arch 2 



Branchial arch j — S 

 Branchial arch 4 



Arytenoid, ridge 



Lateral lingual anlage 



Branchial arch i- 

 Lateral lingual anlage- 



Branchial arch 3 ^ ' \ 

 Branchial arch 4 



Arytenoid ridge 



r 



k''-^. 



Tuherculum impar 



Branchial arch 2 



Epiglottis 

 Glottis 



Fig. 156. — Dissections showing the development of the tongue in pig embryos. X 12. A, 9 mm. em- 

 bryo; B, 13 mm. embryo. 



tuberculum impar is the point of evagination of the thyreoid gland. The copula 

 also connects the tuberculum impar with a rounded prominence which is developed 



