44 
The 
THE DOGS SKUEL. 
THE TEETR: 
teeth while forming no part of the skeleton, 
and having quite a different origin, are so 
closely related to the manillary and mandibular 
arches, and offer such valuable aid in the iden- 
tification and classification, that they may here 
be conveniently described in completing the 
description of the dog’s skull. 
Development: The teeth are developed in the 
The 
mucous membrane of the jaw, the enamel being 
produced from the epithelium (epzb/astec), and 
the dentine, pulp, and cement from the sub- 
epithelial connective tissue (mmesoblastic ). 
first sion ofa tooth im the embryo, 1s an 
involution of the epithelium to form a groove, 
the primitive dental groove, which is filled 
with the imvoluted epithelial cells, “At the 
bottom of this groove, from a series of differen- 
tiated corpuscles in the sub-epithelial tissue, a 
dental papilla is formed. The involuted epi- 
thelial cells increase in number, and certain of 
these become modified, and form a cup over 
the apex of the papilla, and ultimately become 
the enamel organ. The papilla grows, and 
becomes differentiated into formative pulp 
and dentine. Calcification later takes place, 
successive thin layers of dentine forming as 
the -milk teeth -grow. Finally the papilla 
