164 



MICROSCOPIC ANATOMY OF THE ORGANS. 



of the tooth the inner enamel cells develop a cuticle-like bor- 

 der. Toward the dentine the so-called Tomes' processes are 

 sent out, which give rise to the enamel prisms. Finally, calci- 

 fication takes place from the centre to the periphery, both in 

 the prisms and in the cement substance joining them. The 

 enamel cells disappear, the cuticle is pushed to the surface and 

 forms the dental cuticle. 



The development of the cement, which is a product of the 

 inner wall of the tooth sac, takes place later as a sort of peri- 

 osteal bone formation. 



3. The Tongue. 



The tongue is an organ consisting largely of striated 

 muscle. Its mucous membrane, which is a continuation of 

 that lining the mouth cavity, is differentiated in certain places 



FIG. 120. 



Horny epithelium 



Secondary papilla- 



Epithelh 



Tunica propria 



Two filiform papillae from 



X 80. 



in a characteristic fashion. In most animals certain parts of it 

 possess a distinct corneous layer, but the most essential struct- 

 ures are the so-called papillae. In man there are three kinds 

 of these : 



