250 ORIGIN AND DEVELOPMENT OF THE TEETH. 



small papilla, which is the germ of the anterior temporary 

 molar. In the eighth week, the papillas for the canine, in 

 the tenth those for the incisors, and next those for the 

 posterior temporary molars are seen. 



This is styled the first or papillary stage of development. 

 Delicate processes, passing from the sides of the dental 

 grooves, meet in front and behind the papillae, so as to form 

 an open follicle for each. This is the second or follicular 

 stage, which is not completed until the fourth or fifth 

 month. At this period the papillge begin to change their 

 form into that of the future teeth. 



The follicles, which are still open, begin now to be closed, 

 sending from their edges membranous processes across 

 their mouths, called opercula or lids. Two of these oper- 

 cula belong to the incisors, three to the canine, and four 

 or five to the molars. The complete formation of these 

 operculaa constitutes the third or saccular stage, which 

 commences about the fourth month and continues to the 

 period of eruption which is another stage called the erup- 

 tive, and already described in another place. 



During the saccular stage occur some of the most inter- 

 esting phenomena in dental growth. At this period the 



ceding, and its floor, where the pulp is being formed, dilating, fc Cavity of 

 reserve becoming a sac, and temporary tooth a layer of bone. I Temporary 

 tooth rising to the surface of the gums and getting a fang, m Sac of the tem- 

 porary tooth touching the surface of the gums, and its roots elongated, n Sac 

 of the temporary tooth again become a follicle by its eruption, o Completion 

 of the sac, and its free portion becoming the vascular margin of the gum, and 

 the " permanent sac connected by a chord passing through the alveole dental 

 canal or foramen.'' 



FIG. 71, B. a Non-adherent portion of primitive dental groove, b Papilla 

 and follicle upon the floor of this non-adherent portion, now become a part of 

 the secondary groove, c Papilla become a pulp, and the follicle a sac, and 

 cavity of reserve seen, d Sac of first molar advancing into the coronoid pro- 

 cess or tuberosity of superior maxilla, and increased in size, e Sac of first 

 molar having resumed its former position. / Cavity of reserve sending back- 

 wards the sac of the second molars, g Sac of second molar coming into the 

 coronoid process, or tuberosity of superior maxilla, h Sac of second molar 

 returned and cavity of reserve shortened, i Cavity of reserve sending offsac and 

 pulp of the dens-sapientiaj or wisdom tooth, j Sac of wisdom tooth advancing 

 into coronoid process, and tuberosity of the superior maxilla, k Sac of the 

 wisdom tooth returned and forming the last of the dental range. 



