File:Image from page 405 of "On the anatomy of vertebrates (electronic resource)" (1866) (14755253642).jpg

Identifier: b20416039_001 Title: On the anatomy of vertebrates [electronic resource] Year: 1866 (1860s) Authors: Owen, Richard, 1804-1892 Subjects: Anatomy, Comparative Vertebrates Fishes Reptiles Mammals Birds Publisher: London : Longmans, Green Contributing Library: Wellcome Library Digitizing Sponsor: Wellcome Library

View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book

Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image: ycontained in disgregated granules inthe cells, which are thus renderedwhite and opaque, viewed by reflectedlight. The relative density of thedentine and cement varies accordingto the proportion of the earthy material, and chiefly of that partwhich is combined with the animal matter in the walls of thecavities, as compared with the size and number of the cavitiesthemselves. In the complex grinders of the elephant, the maskedboar, and the capybara, the cement, which forms nearly half themass of the tooth, wears down sooner than the dentine. The enamel, fig. 235, <?, is the hardest constituent of a tooth,and, consequently, the hardest of animal tissues; but it consists,like the other dental substances, of earthy matter arranged byorganic forces in an animal matrix. Here, however, the earth ismainly contained in the canals of the animal membrane; and, inmammals and reptiles, completely fills those canals, which are com-paratively wide, whilst their parietes are of extreme tenuity. The

Text Appearing After Image: Magnified section of incisor, Horse ;c cement, d dentine, e enamel, v. DENTAL TISSUES. 361 237 hardening salts of the enamel are not only present in far greaterproportion than in the other dental tissues ; but, in some animals,are peculiarly distinguished by the presence of fluate of lime. Teeth vary in number, size, form, structure, modifications oftissue, position, and mode of attach-ment, in different animals. Theyare principally adapted for seizing,tearing, dividing, pounding, or grind-ing the food; in some they aremodified to serve as weapons ofoffence and defence; in others, asaids in locomotion, means of anchor-age, instruments for uprooting orcutting down trees, or for transportand working of building materials ;they are characteristic of age andsex; and in man they have secondary relations subservient tobeauty and to speech. Teeth are always most intimately related to the food and habitsof the animal, and are therefore highly interesting to the physiol-ogist. They form for th

Note About Images