554 THE HUMAN EMBRYO. 



nasal passages, a pair of short tubes leading from the olfactory pits 

 to the fore part of the roof of the mouth, into which they open 

 in much the same position as the posterior nares in an adult frog. 



At a later stage, after the outgrowth of the median part 

 or bridge of the nose, the two processus globulares meet each 

 other in the median plane, and fuse to form the median part of 

 the upper lip (</. Figs. 207 and 241). 



There are, thus, in the upper lip three sutural lines : a median 

 one, where the inner borders of the two processus globulares 

 meet and fuse with each other ; and a pair of lateral ones, where 



FO 



FO' 



MX' 



MX 



FIG. 241. The roof of the mouth of a Human Embryo about two and a half 

 months old, showing the mode of formation of the palate. (From His.) 

 xlO. 



FO, processus jrlobularis. 3TO', palatal process of prooessus globularis. MX, 

 maxillary arch MX', palatal process of maxillary arch. OB, mouth cavity. OD, 

 eye. OK, aperture of olfactory pit, or nostril. OL, lens. 



the outer borders of the processus globulares meet and fuse with 

 the inner ends of the maxillary arches. 



The median cleft is the one which persists throughout life 

 in the hare or rabbit, but it is doubtful whether it ever remains 

 open in man ; what is called hare- lip in man being due to imper- 

 fect closure of one or other of the lateral clefts. 



The palate is formed, as regards its most anterior portion, 

 by a pair of horizontal shelf-like outgrowths from the pro- 

 cessus globulares (Fig. 241, FO'), which meet and fuse in the 

 median plane. The rest of the palate, comprising the greater 

 part of its length, is formed by two similar outgrowths, MX', from 



