314 



THE TEETH. 



coats which afterwards are formed. From the bottom a papilla (p) 

 meanwhile rises, soon becoming vascular, and assuming the shape of 



Fiff. 214. 



\ 



■C<^^-:- 



:i-., L. 



Fig. 214. — Diagrams of the Mode of Origin uf the Dental Germ in the 

 Ruminant (after Kollikei-). 



The three figures represent transverse sections of the gum and a part of the jaw at or 

 .shortly after the period of the formation of the germ, and are designed chiefly to show 

 the relation o tlie germ to the epithelium. 



A, represents a very early condition, when the enamel-germ of a milk or temporary 

 tooth has been formed by a down-growth of the deep layer of the epithelium. 



15, represents a later stage, when the tooth-papilla has risen from the surface of the 

 mucous membrane, and has indented the enamel-germ. 



C, represents a more advanced stage in which the dental sac has begun to be formed. 



c, the superficial thick epithelium of the gum only sketched in outline ; c', the deep 

 layer ;/, the epithelial downgrowth ; /', the special enamel-germ, afterwards (in B and 

 C) the enamel-organ ; p, the dental papilla, and afterwards tooth-pulp. In B and C a 

 clear space is seen between the dental pulj) and the deeper columnar cells, c, of the 

 enamel-organ : it is probably produced by a shrinking of the soft parts away from one 

 another ; s, the commencement of the dental sac ifp, the enamel-germ of the correspond- 

 ing permanent tooth. 



