. Text-book of normal histology: including an account of the development of the tissues and of the organs. al pa-pilla (/), at whose summit osteoblasts {d) areforming young dentine (c); inner layer {a) ofenamel organ is engaged in producing layer ofyoung enamel (b); e, middle, h, outer layer ofenamel organ. THE DIGESTIVE TRACT. 153 Fig. I fibres ; the canals left within the matrix to maintain the nutritionof the tissue constitute the dentinal tubules, the homologues ofthe lacunae and canaliculi of the continued growth the sidesof the papill^ as well as the apex be-come covered by the
. Text-book of normal histology: including an account of the development of the tissues and of the organs. al pa-pilla (/), at whose summit osteoblasts {d) areforming young dentine (c); inner layer {a) ofenamel organ is engaged in producing layer ofyoung enamel (b); e, middle, h, outer layer ofenamel organ. THE DIGESTIVE TRACT. 153 Fig. I fibres ; the canals left within the matrix to maintain the nutritionof the tissue constitute the dentinal tubules, the homologues ofthe lacunae and canaliculi of the continued growth the sidesof the papill^ as well as the apex be-come covered by the layer of newly-formed dentine ; the central part ofthe dental papilla remains, after allthe dentine has been formed, as thepulp-tissue, into which the blood-vessels and nerves grow at a laterperiod. At first both dentine and enamelare soft, the impregnation with limesalts occurring subsequently; thelayer of the soft, most recentlyformed matrix is readily distin-guished in stained sections from theolder calcified tissue. The cemen-tum, wanting during foetal life, isproduced by the alveolar THE TONGUE. Section of developing tooth from cat em- •bryo, portion of preceding figure more highlymagnified : fn, mesodermic elements consti-tuting pulp-tissue; /, layer of odontoblasts en-gaged in producing dentine (/i); a and b, cellsof middle layer, c and d, cells of inner layerof enamel organ ; e, zone of young enamel. The bulk of the tongue is com-posed of variously-disposed bundlesof striated fibres of the lingualis,together with those of the accessory muscles, over the unattachedsurfaces of which the oral mucous membrane is reflected. Themuscular tissue of the organ is arranged in bundles extending inthree planes : (i) vertically and slightly radially (genio-hyoglossus,vertical fibres of lingualis and hyoglossus) ; (2) transversely (trans-verse fibres of lingualis) ; (3) longitudinally (lingualis superior andinferior, and styloglossus), A vertical median partition, the
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherphiladelphiajblipp
