THE ALIMENTAKY CANAL AND ITS APPENDAGES 



HUMAN 



PALATAL KIDGES 



THE mucous membrane of the roof of the mouth is thrown into 

 a more or less marked median ridge the raphe, and into a 

 varying number of paired transverse ridges (r.p., Fig. 95), which 

 are especially well developed an- 

 teriorly near the incisors, but pos- 

 teriorly become flattened out. There 

 are five to seven of these transverse 

 palatal ridges on each side, and they 

 are more developed in the embryo 

 and the new-born child than in later 

 life, when their primarily regular 

 arrangement disappears. Those 

 farthest back degenerate, but the FIG. 95. PALATE OF 

 anterior ones increase in size and 

 shift nearer to one another as age 

 advances. In very aged persons 

 the whole system of ridges may almost, 

 disappear. 



In these ridges which, as has been seen, vary to a great extent, 

 we have the representatives of a larger and more numerous series 

 met with in many lower Mammals (cf. Fig. 96) (in Apes there 

 are as many as ten). They are, as a rule, covered with a tough 

 stratified epithelium, and are functional in helping to triturate 

 and crush the food taken into the mouth (Gegenbaur). 



Some years ago I called attention to the fact that in the 

 embryo Cat these ridges develop as rows of papillae, which later 

 unite, and I put forward the suggestion that we may be here 

 dealing with the remains of palatal teeth handed down even to 

 Man. Closer investigation must show whether these papillae are 

 actual vestiges of tooth structures or only horny growths, such 



tina ; al., the later formed alveolar 



even altogether, 



