38 STAGES OF DENTITION. 



during which, the follicle or sac does not exist, and the 

 future pulp is a simple papilla on the free surface of 

 the gastro-intestinal mucous membrane ; this papillary 

 stage being; of short duration, was included under the 

 follicular. About the sixth week of embryonic life he 

 found a depression or groove in the form of a horse- 

 shoe along the edge of the jaw in the mucous 

 membrane of the gum, and this he named the primitive 

 dental groove, as the germs of the teeth first appear in 

 it. By the thirteenth week a series of ten papillae arose 

 in succession in each jaw, constituting the germs or 

 rudimentary pulps of the milk-teeth, and which he 

 viewed as processes of the mucous membrane itself. 

 Each papilla adhered by its base to the fundus of the 

 groove, whilst its apex, up to the eleventh or twelfth 

 week, presented itself at, or protruded from, the mouth 

 of its follicle. The upper jaw was earlier than the 

 lower one in respect to this stage. 



The follicles appeared to Goodsir as mere dupli- 

 catures of the membrane of the groove, or the general 

 gastro-intestinal mucous membrane passing across and 

 between the papilla?. Each of the individual follicles, 

 with its papilla, vascular branches, and nervous twig, 

 exactly resembled a large hair-bulb, with its nerve and 

 vessels exposed after the hair has been extracted.""" As 



* This opinion receives confirmation now that the teeth and the hairs 

 rank as homologous organs. Professor Huxley viewed them either as hoth 

 enderonic, or hoth ccderonic. The "basement membrane" being found an 

 imperfect test, Huxley, guided by the question of growth, considers the hair, 

 the teeth, the scales of fish, and probably the "dermal plates" of reptiles as 

 ecderonic organs.— Supplement to Cyclopaedia of Anatomy and Physiology, p. 

 ■170. 



