TEETH TUMOURS. 



43i 



The formation of these partitions places each papilla in a' 

 'separate cavity ; and concurrent with this process, small growths 

 take place upon the membrane of the mouth just as it dips 

 into the papillary cavity or follicle, which finally, by union 

 with other growths, form a lid which covers the papiUaa in a 

 closed sac or bag. 



Before the final closing of the foUicle, a slight folding inwards" 

 of its lining membrane takes place. 



This folding inwards of the membrane of the primitive groove 

 is for the purpose of forming a new cavity — the cavity of rcscrxe 

 — which furnishes a delicate mucous membrane for the future 

 formation of the permanent teeth. By consulting the diagram 

 the reader will better understand this process. Fig. 1 shows the 



FiQ. 86. 



pal^illa standing in the groove, and a slight folding inwards of 

 the membrane of the primitive groove near to the lid on the 

 riuht side. Fig. *? mokes this more apparent ; and in the other 

 Figa. we find the fQlded membrane considerably altered in form, 

 and increased in size, liaving a projection from its bottom part, 

 — tlie papilla destined for the production of the permanent tooth 

 detadied from its follicle.— (From Simoxds On the Afje of the Ox. 

 &c, 1854.) 



From a study of this, it will be found that the ca\-ity in 

 ; which the permanent tooth is developed is a mere detaohment 

 k from the lining of the primitive groove, by the formation of a. 



