DENTIN 325 DENVER DENTIN, or DENTINE, that tissue which forms the body of the tooth, the others being cement, which forms the outer crust; and enamel, which (when present) is situated between the dentin and the cement. It is composed of an organized animal basis, arranged in the form of minute tubes and cells of earthy particles. DENTIROSTRES, a tribe of birds of the order Insessores, or perchers; so named from having a notch near the tip of the beak in the upper mandible. They include the shrikes, butcher-birds, etc. The tribe is divided into the following families: (1) Laniidas (shrikes), (2) Ampelidse (chatterers), (3) Muscicapxdse (fly-catchers), (4) Turdidae {thrushes), and (5) Sylvidse (warblers). DENTISTRY, the art of cleaning and extracting teeth, of repairing them when diseased, and replacing them when neces- sary by artificial ones. There are two very distinct branches of the art now rec- ognized, one being dental surgery, the other mechanical dentistry. The first re- quires an extended medical knowledge on the part of the practitioner, as, for in- stance, a knowledge of diseases the ef- fects of which may reach the teeth, of the connection between the welfare of the teeth and the general system, etc., as well as ability to discern latent oral dis- eases, calculate the effects of opera- tions, etc. The second department, mechanical dentistry, is concerned with the construc- tion of artificial substitutes for lost teeth, and requires much mechanical science, it being a very delicate work to give arti- ficial teeth a perfectly natural appear- ance in shape and color. In the United States the Baltimore College of Dental Surgery is the oldest, its charter being dated 1839; the Ohio College of Dental Surgery followed in 1845; the Philadel- phia College of Surgery in 1850; the Philadelphia Dental College in 1863; the New York College of Dentistry in 1865, and various others. The "American Journal and Library of Dental Science" was established in Baltimore in 1839. Every State has now its State Dental Society; besides national organizations, of which the American Dental Associa- tion is among the most important. DENTON, a city of Texas, the county- seat of Denton co. It is on the Missouri, Kansas and Texas, and the Texas and Pacific railroads. It is an important trading point for cotton, wheat, corn, and cattle. The city is the seat of the North Texas State Normal College, and the Col- lege of Industrial Arts. Pop. (1910) 4,732; (1920) 7,626. D'ENTRECASTEAUX ISLANDS (don-tr-kas-to'), since 1884 part of the British protectorate of New Guinea, lie N. of the S. E. extremity of New Guinea. With an area of 1,083 square miles, they comprise three chief islands separated by narrow channels. They are named after the French admiral and explorer, Bruni D'Entrecasteaux (1739-1793), who vis- ited these waters in 1792. His name is also preserved in D'Entrecasteaux Point on the S. W. coast of Western Australia; and in D'Entrecasteaux Channel, sepa- rating the S. of Tasmania from Brune Island. DENUDATION, the act of making naked or bare; a stripping or denuding. In geology, the laying bare by removal of superficial matter so as to disclose the subjacent strata; so also is the removal by water of any formation or part of a formation. Thus we hear of denuded rocks or of a strata removed by denuda- tion. In medicine, the word is applied to the condition of a part deprived of its natu- ral coverings, whether by wound, gan- grene, or abscess. It is particularly ap- plied to the bones when deprived of their periosteum, and to the teeth when they lose their enamel or dental substance. A valley of denudation is a valley formed by the denudation of the strata in which it is hollowed out. DENVER, the capital of Colorado, the county-seat of Denver co. It is at the junction of the South Platte river and Cherry creek, and on the Santa Fe, the Colorado and Southern, the Burlington, the Denver and Salt Lake, the Rock Island, and the Union Pacific railroads. Denver is the logical distributing point for territory extending over 1,700 miles east and west and over 1,600 miles north and south and containing a population of approximately 21,000,000 people. The city is situated at an altitude of one mile above sea-level and it is within 15 miles of the eastern base of the Rocky Moun- tains. On account of the remarkable clearness of the atmosphere and the mild- ness of the climate, Denver makes an especially desirable residence for persons suffering with pulmonary complaints. It has an area of over 60 square miles. Al- though the city is distinctly residential, it is also an important industrial center. It has a manufacturing output of over $100,000,000 annually. Its proximity to the important great mining regions of Colorado makes it the central distribut- ing point for this region. Mining ma- chinery is manufactured on a large scale. There are large stock yards comprising pi^re than 150 acres and representing an =-•- >stment of nearly $15,000,000. It is
