64 



SPECIAL HISTOLOGY. 



teeth, are aggregations of epithelium, and are probably patho- 

 logical 1 (see Mikr. Anat. II. 2, p. 92). 



[The dental sacs consist of connective tissue, in which ves- 

 sels and nerves are distributed; from their base proceeds the 

 dental pulp, which, in form, resembles the tooth to which it 



Fig. 196. 



belongs, and consists of an internal portion rich in vessels, 

 and eventually in nerves also, and of a non-vascular external 

 portion. The latter is bounded by a delicate structureless 

 membrane, the membrana praformativa (Raschkow), which has 

 no further relation to the development of the tooth. Beneath 

 this, lie cells of 0-016— 0-024"; in length, and 0002—0-0045 



Fig. 196. A, tooth-sac of the second incisor of an eight-months' foetus, from 

 the broad surface, x 7 : a, dental sac ; b, enamel pulp ; c, enamel membrane ; 

 d, enamel ; e, dentine ; f, dentinal cells ; g, limits of the cap of dentine ; h, dental 

 pulp ; i, free edge of the enamel organ. B, first incisor of the same embryo from 

 the narrow surface : letters as before ; a, dentinal cap in toto ; Jc, nerves and vessels 

 of the pulp. 



1 [They have a diameter of from 024 — 0-36'", and are composed throughout of 

 numerous concentric layers of ordinary epithelial plates, or of softer scales, with 

 cholesterine crystals and granules. Besides these, microscopic bodies of 002 — 0-12'", 

 soft, and with only indications of lamination, are found in the gum (Kblliker, 1. c.) 

 The true nature of these glands was pointed out by Purkinje and Raschkow. — Eds.] 



