88 



GENERAL HISTORY OF DEVELOPMENT 



During the sixth week the maxillary processes fuse with the lateral nasal and 

 mesial nasal processes to form the cheeks, the lateral parts of the upper lip (fig. 125), 





FIG. 123. HEAD OF AN EMBRYO ABOUT 

 TWENTY-NINE DAYS OLD, FROM 



BEFOEE. (His.) 



pr.glob., globular extremity of the 

 mesial nasal process ; mx, maxilla; mn, 

 mandible; hy, hyoid arch; br', first 

 branchial arch. 



FIG. 124. HEAD OF AN EMBRYO ABOUT 



THIRTY-FOUR DAYS OLD. (His.) 



i.m,, placed on the frontal-nasal process and 

 just above its intermediate depressed part ; 

 l.n.pr., lateral nasal process ; m.n.pr., mesial nasal 

 process ; pr.glob., as in the 'previous figure. 



FIG. 125. HEAD OF AN EMBRYO OF ABOUT 



SEVEN WEEKS. (His.) 



The external nasal processes have united 

 with the maxillary and globular processes 

 to shut off the olfactory pit from the orifice 

 of the mouth. 



FIG. 126. HEAD OF AN EMBRYO 

 AT THE END OF THE SECOND 

 MONTH, WITH THE PARTS OF 

 THE NOSE AND MOUTH BEGIN- 

 NING TO ASSUME THEIR PER- 

 MANENT RELATIONSHIPS. (His.) 



and the alse of the nose ; while by the end of the second month the mesial nasal 

 processes fuse with one another to form the mesial part of the upper lip and the 



