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46 SALIVARY CALCULUS. ibility) is readily absorbed by the tissues or goes to form new- compounds, necessitating a precipitation of the calcarious mat- ter. * * * Calcarious matter may be deposited in either a fibrous or fluid matrix." There can be no doubt that material environments may exert a great influence on the character, quantity and rapidity of accumulations of tartar upon the teeth of individual subjects. There are mechanical conditions that conduce to the forma- tion of scales of tartar upon the teeth. Practitioners daily ob- serve mouths wherein for some reason, perhaps a habit, or owing to a deformity, or to a weakness of the jaw or muscles of mastication, due to disease or accident, there has been a failure to employ a large portion of the teeth in mastication. In such instances experience teaches us to anticipate extensive deposits of calcarious matter upon the unused teeth. But we do not always find it so j the fact remains, and unexplained, that some individuals are blessed with immunity from deposits of dental tartar, notwithstanding that they are utterly negli- gent of the sanitary condition of their mouths, which per- haps may be accounted for by their thoroughly employing their teeth in mastication of food ; all of which is in evident accordance with creative economy, and therefore correct. It would be interesting to know certainly, to what extent and in what way the state of health of the individual may or does modify the tendency to deposition of lime upon the teeth. The healthiest appearing subjects often present the most an- noying predisposition to such deposits, while it is a fact well known among dentists that consumptives are but little an-