ORIGIN OF THE DENTAL GERMS. 



795 



Fig. 553. DIAGRAMS OF THE MODE OP 

 ORIGIN OF THR DENTAL GEKM IN 

 THE RUMINANT (after Kolliker). 



The three figures represent trans- 

 Terse 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 of 

 the germ to the epithelium. 



A, represents the state in a very 

 early condition, when the primitive 

 deutal follicle of a milk or temporary 

 tooth has been formed by a depression 

 from the deep layer of the epithe- 

 lium. 



B, represents a later stage, when the 

 tooth-papilla has risen from the surface 

 of the mucous membrane, and has 

 inflected the primitive dental follicle. 



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 of cylindrical cells ; /, 

 the primitive tooth -follicle ; /', its cel- 

 lular or granular contents and cavity ; 

 p, the dental papilla, and afterwards 

 tooth-pulp ; e, the inner inflected layer 

 of the wall of the primitive follicle 

 forming the inner part of the enamel 

 organ ; e', the outer wall of the same 

 with the epithelial sprouts shooting into 

 the tissue above ; s, the commencement 

 of the dental sac ; fp, the follicle of 

 the corresponding permanent tooth. 



Waldeyer has shown by more 

 recent observations, that in the 

 human embryo the teeth arise in a 

 manner essentially the same as that 

 described by Kolliker in the rumi- 

 nant. (Waldeyer, lib. die Entwick. 

 <ler ZShne, Zeitsch. fur. ration. Me- 

 dicin, 1865, and Henle's Bericht, &c. 

 for 1864, p. 81.) 



The dental sacs, after the 

 closure of the follicles, continue 

 to enlarge, as do also their con- 

 tained papillae. The walls of 

 the sacs, which soon begin to 

 thicken, consist of an outer tibro- 

 areolar membrane, and an in- 

 ternal highly vascular layer, 

 lined by epithelium ; their blood- 

 vessels are derived partly from 

 the dental arteries which course 

 along the base of the sacs, and 

 partly from those of the gums. 



The papillse, now the dental 

 pulps, acquire a perfect resem- 



Fig. 553. 





