DEVELOPMENT OF THE FACE. 



mandibular to unite with the maxillary element. Any of these 

 processes may be under or over developed ; over-development of 

 the nasal and under-development of the mandibular (micro- 

 gnathia) are of common occurrence. 



THE NASAL PROCESSES. 



The nasal process at a very early stage is seen to be 

 divided into two lateral processes and two mesial, the latter 

 having globular enlargements as tips (Fig. 1). It must be re- 

 membered that the lateral and mesial nasal processes are really 



crista galli 



vertical plate of ethmoid 



position ofcanalis cranio- 

 pharyngeus. 



sept. cart. 



alar 



carta. \\. , , , - : — uom er. 



^naso-palatine canal 

 premaxilla 

 mesial port, of upper lip. 



Fig. 3. — Showing the structures formed in the Mesial Nasal Processes, 



vertical septa springing from the basis of the primitive capsule 

 of the fore-brain, and the parts seen on the face are the anterior 

 extremities of these septa (see Fig. 8). 



What become of the Mesial Nasal Processes. — From the 

 mesial nasal processes, which fuse together, and may enclose 

 epithelial remnants between them, are formed the whole septum 

 of the nose (Fig. 3), the premaxillary part of the upper jaw 

 and the middle third of the upper lip (Fig. 2). It contains a 

 skeletal basis of cartilage, formed by the trabeculae cranii (Figs. 

 135, 136, p. 168). 



Structures formed in the Mesial Nasal Processes. — The 



