54 



CONNECTIVE TISSUE. 



lines the alveolus and -holds the tooth in its place. It is here 

 called pericementum. 



Development of Teeth (Figs. 42-45). About the seventh week 

 of fetal life the germinal epithelium which covers the mucous mem- 

 brane of the gums of the embryo, grows so as to form an elevated 

 ridge, the maxillary rampart. A similar growth occurs downward 

 into the tissue of the mucous membrane, forming the common 

 dental germ or dental lamina. From this lamina ten cellular proc- 

 esses, the special dental germs, are given off in each jaw, corre- 

 sponding to the number of teeth. Each special germ becomes 



21 Enamel-cells. 



Mi 



rF ""Odontoblasts. 



FIG. 47. A portion of a cross-section through a developing tooth (later stage 

 than in Fig. 45) ; X 720 (Bohm and Davidoff). The den tin is formed, but has 

 become homogeneous from calcification. Bleu de Lyon differentiates it into zones 

 (a and 6). At c is seen the intimate relationship of the odontoblasts to the tissue 

 of the dental pulp. 



flask -shaped, and later flattened, and still later indented on its 

 under side. The special germ becomes the enamel-organ of the 

 future tooth, as from it the enamel is produced. From the corium 

 of the mucous membrane grows a vascular papilla, the dental 

 papilla, which, as it grows, increases the indentation of the special 

 germ and is covered by it. This papilla becomes the dentin and 

 pulp of the tooth, the odontoblasts which cover it forming the 

 dentin and the other portion the pulp. From the tissue which 

 produces the papilla a vascular sac, the dental sac, is formed, 

 which surrounds the special germ and its papilla. The dental sac 

 and all the structures within it constitute the dental follicle. 



