488 



SPECIAL HISTOLOGY. 



following order : first molar in the seventh year, inner incisor in the 

 eighth year, lateral incisor in the ninth year, first premolar in the tenth 

 year, second premolar in the eleventh year, canine in the twelfth year, 

 second molar in the thirteenth year, third molar (wisdom tooth), between 

 the seventeenth and nineteenth years. 



The gum in the foetus, and especially in newly born infants before 

 the eruption of the milk teeth, is whitish and very firm, almost cartila- 

 ginous, whence perhaps it has also been called gum-cartilage, although 

 it has not the slightest resemblance to cartilage in structure, but consists 

 of the ordinary elements of mucous membrane, but with a considerable 

 admixture of a more tendinous tissue. The bodies of the size of millet- 

 seed, contained in it, described by Serres, the so-called glandulce 



Fig. 196. 



tartaricce, which are supposed to secrete the " tartar " of the teeth, are 

 aggregations of epithelium, and are probably pathological* (see Mikr. 

 Anat. II. 2, p. 92). 



The dental sacs consist of connective tissue, in which vessels and nerves 

 are distributed ; from their base proceeds the dental pulj), which, in 



Fig. 196. — -./^j tontli-sac of the second incisor of an eight-months' foslus, from the broad 

 surface, magnified 7 diameters: a, dental sac: b, enamel pulp; c, enamel membrane; d, 

 enamel ; e, dentine ; _/, dentinal cells ; g, limits of the cap of the 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 ioto ; k, nerves and vessels of the pulp. 



* [They have a diameter of from 0'24-0'3G of a line, and are composed throughout of 

 nvimerous concentric layers of ordinary epithelial plates, or of softer scales, with cholesterine 

 crystals and granules. Besides these, microscopic bodies of 0-02-0-12 of a line, soft, and 

 with only indications of lamination, are found in the gum (KoUiker, 1. c). The true nature 

 of these glands was pointed out by Purkinje and Raschkow. — Trs.] 



