The great majority of drugs have no injurious effect upon the teeth. Some medicines, however, must be used with great care. The acids used in the tincture of iron have a great affinity for the lime salts of the teeth. As this form of iron is often used, it is not unusual to see teeth very badly stained or decayed from the effects of this drug. The acid used in the liquid preparations of quinine may destroy the teeth in a comparatively short time. After taking such medicines the mouth should be thoroughly rinsed with a weak solution of common soda, and the teeth cleansed. 170. Alcohol and Digestion. The influence of alcoholic drinks upon digestion is of the utmost importance. Alcohol is not, and cannot be regarded from a physiological point of view as a true food. The reception given to it by the stomach proves this very plainly. It is obviously an unwelcome intruder. It cannot, like proper foods, be transformed into any element or component of the human body, but passes on, innutritious and for the most part unappropriated. Taken even into the mouth, by any person not hardened to its use, its effect is so pungent and burning as at once to demand its rejection. But if allowed to pass into the stomach, that organ immediately rebels against its intrusion, and not unfrequently ejects it with indignant emphasis. The burning sensation it produces there, is only an appeal for water to dilute it. The stomach meanwhile, in response to this fiery invitation, secretes from its myriad pores its juices and watery fluids, to protect itself as much as possible from the invading liquid. It does not digest alcoholic drinks; we might say it does not attempt to, because they are not material suitable for digestion, and also because no organ can perform its normal work while smarting under an unnatural irritation. Even if the stomach does not at once eject the poison, it refuses to adopt it as food, for it does not pass along with the other food material, as chyme, into the intestines, but is seized by the absorbents, borne into the veins, which convey it to the heart, whence the pulmonary artery conveys it to the lungs, where its presence is announced in the breath. But wherever alcohol is carried in the tissues, it is always an irritant, every organ in turn endeavoring to rid itself of the noxious material.