Veterinary obstetrics, including the diseases of breeding animals and of the new-born . , in someteeth, there grow out projections or septa of dentine, to consti-tute the roots or fangs, which divide this cavity into two ormore distinct openings, according to the individual tooth orspecies, and, through these apertures, the blood vessels andnerves pass to the pulp of the tooth. See Fig. 44. As the enamel organ sinks down into the jaw, there occurs of the surrounding mesoblastic connective tissue toconstitute a capsule, the tooth follicle, which closely invests theenamel organ an
Veterinary obstetrics, including the diseases of breeding animals and of the new-born . , in someteeth, there grow out projections or septa of dentine, to consti-tute the roots or fangs, which divide this cavity into two ormore distinct openings, according to the individual tooth orspecies, and, through these apertures, the blood vessels andnerves pass to the pulp of the tooth. See Fig. 44. As the enamel organ sinks down into the jaw, there occurs of the surrounding mesoblastic connective tissue toconstitute a capsule, the tooth follicle, which closely invests theenamel organ and papilla. When the bony tissue of the jawforms, the follicle serves as periosteum for the tooth and alveolus,while, from its inner layers, the external tooth tissue, thecement, is developed. The origin of the dental tissues is then :I, the enamel from the invaginated epiblastic cells; 2, the pa-pilla, vessels, nerves and dentinal tubules from the mesoblastic The Teeth 313 connective tissue, and, 3, the cementum and dental and alveolarperiosteum from the mesoblastic dental Fig. 44. Sagittal section through an inferior grinder of an equineembryo, 4 inches long. ect, ectoderm of mouth cavity ; mes,mesoderm; eo, enamel organ ; ec, enamel cells ; d, den-tine ; eb, embryonic bone. The enamel cap is at most points detached from the dentinepapillae. The .section through the tooth follicle is so made thatthe plicae of the enamel cap have split each of the dentinepapillae so that there are four instead of two. When the bony jaws form later, the teeth are at first in con-tinuotis grooves, but transverse osseous partitions later extendbetween the tooth germs and finall} constitute separate compart-ments, or alveoli, for each. The permanent teeth are developedas outgrowths from the enamel organs of the temporary set inthose cases where they are preceded by such; in the others theyare formed the same as the temporary teeth from a backwardgrowth of the common enamel germ. The teet
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectveterinaryobstetrics
