THE DEVELOPMENT OF THE TEETH. 143 



While these changes are going on, the tooth sac is becoming 

 lodged in a widely open gutter of bone, which is being rapidly 

 formed at its sides and under its base. If at this stage 

 (see Fig. 69) the gum be stripped off the jaws, the 

 developing tooth capsules are torn off with it, from 

 which they are inseparable except by actual cutting, thus 

 leaving the gutter of bone quite bare and empty. In fact 

 the capsule or sac which encloses the tooth germ consists of 

 almost the whole of the connective tissue which intervenes 

 between the special dentine and enamel germs and the bone. 



In the first instance the follicle wall is only distinguished 

 from the connective tissue external to it by being somewhat 

 richer in cells, vessels, and fibrillar elements ; being, in fact, 

 more condensed or more compact. The sacs, when at their 

 fullest development, are divisible into two layers, an outer 

 thin firm wall, and an inner looser tissue, not very dense. At 

 the base of the tooth sac, the follicle wall is not separable 

 nor distinguishable from the base of the dentine papilla 

 with which it blends. The follicle wall is richly vascular ; 

 and over the surface of the enamel organ it is prolonged 

 inwards in the form of villous or papilliform eminences (8 

 in Fig. 69), projecting into the external epithelium of the 

 enamel organ ; to these prominences, which are analogous to 

 the papillae on the free surface of the gum, some authors 

 attach much importance, as having an influence upon the 

 direction of the enamel prisms, and so regulating the 

 pattern formed ; but this view is by no means universally 

 accepted. The internal or softer and looser portion of the 

 follicle wall, which has a consistency but little firmer than 

 that of the stellate reticulum of the enamel organ, is much 

 developed in Ruminants, where there is to be a deposition 

 of coronal cement. This differentiation of a portion of the 

 dental sac is thought by Messrs. Legros, Robin, and Magitot 

 to be sufficiently pronounced to justify its designation as a 

 distinct " cement organ." 



