120 



TEXT-BOOK OF EMBRYOLOGY. 



develop on each side from the naso-frontal, one, the medial nasal process, 

 near the median line and the other, the lateral nasal process, more laterally. 

 Between the two processes the nasal pit marks the entrance to the future 

 nasal cavity (nostril). The maxillary process grows farther toward the 



Nasal fossa 



Naso-optic furrow 4- 

 Mouth slit~~| 



Branchial groove I 



Cerebral hemisphere 



Naso-frontal process 



'Lateral nasal process 

 Medial nasal process 

 Maxillary process 



Mandibular process 



FIG. 98. Ventral view of head of 13.7 mm. human embryo. His. 



medial line and forms contact with the lateral and medial nasal processes 

 (Figs. 96 and 97). 



Further development consists essentially of fusions between the various 

 elements already present and of changes in the relative proportions of these 



Branchial groove I 

 (external ear) 



Nose ~ 



Lat. nasal process 

 Maxillary process 



Med. nasal process 



FIG. 99. Ventral view of head of human embryo of 8 weeks. His. 



elements. The two medial nasal processes come close together to form a 

 single medial process which gives rise to the middle portion of the upper lip 

 and the adjacent portion of the nasal septum (Figs. 98 and 99). The maxil- 

 lary process expands generally to form the cheek and lateral portion of the 



