. Text-book of normal histology: including an account of the development of the tissues and of the organs. Section of human tooihjunction of the dentine and thecementum: D, dentine with itstubules, which communicate withinterglobular spaces {B i and withlacunae of cementum (C). THE DIGESTIVE TRACT. 149 Fig. 178. pany the larger blood-vessels as meduUated fibres ; these give offfilaments which pass to the layers of odontoblasts, among whichthey extend as pale fibres. The ulti-mate distribution of these latter is stillunsettled ; the assertion that fine fibrillaeaccompany the dentinal fibres int
. Text-book of normal histology: including an account of the development of the tissues and of the organs. Section of human tooihjunction of the dentine and thecementum: D, dentine with itstubules, which communicate withinterglobular spaces {B i and withlacunae of cementum (C). THE DIGESTIVE TRACT. 149 Fig. 178. pany the larger blood-vessels as meduUated fibres ; these give offfilaments which pass to the layers of odontoblasts, among whichthey extend as pale fibres. The ulti-mate distribution of these latter is stillunsettled ; the assertion that fine fibrillaeaccompany the dentinal fibres into thetubules lacks confirmation. Distinct lymphatic vessels havenot been demonstrated within the pulp,although the clefts within the matrixbetween the connective-tissue fibresrepresent the lymph-spaces and are inclose relation with the adjacent lym-phatic channels. DEVELOPMENT OF THE Section of young tooth of child, show-ing peripheral portion of pulp and ad-joining dentine: b, pulp-cells, some ofwhich send processes {a) within dentinaltubules ; c, stroma of delicate connectivetissue; d, blood-vessels. Fig The teeth of man and the higheranimals are really exaggerated papillae,the peripheral parts of which havebecome specialized and have under-gone calcification. The ectoderm con-tributes the enamel, while the dentine,cementum, and pulp are derived fromthe mesoderm. A linear thickening of the primitiveoral epithelium marks the earliest indication of the formation of theteeth ; in man this band appears before the end of the sixth week(Rose), and is adherent to the under surfaceof the epithelial layer. Following the ex-pansion of this ectodermic thickening a con-tinuous lateral projection, the dental ridge,grows obliquely into the mesodermic dental ridge continues to grow back-ward towards the mandibular articulation,forming an unbroken arch of ectodermict
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