THE DEVELOPMENT OF THE TONGUE 



159 



tion in a plane parallel to the first (Fig. 150, III). Place the ventral portion of 



the head in a watch-glass of alcohol and, under the dissecting microscope, remove 



that part of the preparation cranial to the 



mandibular arches. Looking down upon the 



floor of the pharynx, remove any portions of 



the lateral pharyngeal wall which may still 



interfere with a clear view of the pharyngeal 



arches as seen in Fig. 151. Permanent mounts 



of the three stages mentioned above may be 



made and used for study by the student. 



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 thicken- 

 ings of the mandibular arches, both of which are present in human embryos 

 of 5 mm. (Fig. 152 A). At this stage, a median ventral elevation formed by 



FIG. 150. 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. 



Br. arch I 



Tuberculum impar ' 



Br. arch II 



Br. arch III 

 Br. arch IV 



Arytenoid ridge 



Lateral lingual anlage 



Br. arch I 

 Lateral lingual anlage 



Br. arch III 

 Br. arch IV 

 Arytenoid ridge 



Tuberculum impar 



Br. arch II 



Epiglottis 

 Glottis 



FIG. 151. Dissections showing the development of the tongue in pig embryos. A, g mm. embryo; 



B, 13 mm. embryo. 



