A system of human anatomy, general and special . he apex of each fang withthe dental vessels and nerves. The number of roots appears todepend upon the number of nervous filaments sent to each the formation of the ivory has commenced, the enamel organbecomes transformed into a laminated tissue, corresponding withthe direction of the fibres of the enamel, and the crystalline substanceof the enamel is secreted into its meshes by the vascular lining ofthe sac. The cementum appears to be formed at a later period of life, eitherby a deposition of osseous substance by that portion of the de
A system of human anatomy, general and special . he apex of each fang withthe dental vessels and nerves. The number of roots appears todepend upon the number of nervous filaments sent to each the formation of the ivory has commenced, the enamel organbecomes transformed into a laminated tissue, corresponding withthe direction of the fibres of the enamel, and the crystalline substanceof the enamel is secreted into its meshes by the vascular lining ofthe sac. The cementum appears to be formed at a later period of life, eitherby a deposition of osseous substance by that portion of the dental sac,which continues to enclose the fang, and acts as its periosteum, orby the conversion of that membrane itself into bone; the former sup-pcsition is the more probable. The formation of ivory commences in the first permanent molarpreviously to birth. * a. Capsule of a temporary incisor with the rudiment of the corresponding- permanenttooth attached, b. Capsule of a molar in the same state. A part of the gum is seenabove it and in TEETH-ERUPTION. 105 Eruption.—When the crown of the tooth has been formed andcoated with enamel, and the fang has grown to the bottom of itssocket by the progressive lengthening of the pulp, the formation ofivory, and the adhesion of the ivory to the contiguous portion of thesac, the pressure of the socket causes the reflected portion of the sacand the edge of the tooth to approach, and the latter to pass throughthe gum. The sac has thereby resumed* its original follicular con-dition, and lias become continuous with the mucous membrane of themouth. The opened sac now begins to shorten more rapidly thanthe fang lengthens, and the tooth is quickly drawn upwards by thecontraction, leaving a space between the extremity of the unfinishedroot and the bottom of the socket, in which the growth and comple-tion of the fang is more speedily effected. During the changes which have here been described as takingplace among the dental sacs contained
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectanatomy, bookyear1847
