63. Effect of Tobacco upon the Bones. Another narcotic, the destructive influence of which is wide and serious, is tobacco. Its pernicious influence, like that of alcohol, is peculiarly hurtful to the young, as the cell development during the years of growth is easily disturbed by noxious agents. The bone growth is by cells, and a powerful narcotic like tobacco retards cell-growth, and thus hinders the building up of the bodily frame. The formation of healthy bone demands good, nutritious blood, but if instead of this, the material furnished for the production of blood is poor in quality or loaded with poisonous narcotics, the body thus defrauded of its proper building material becomes undergrown and enfeebled. Two unfavorable facts accompany this serious drawback: one is, that owing to the insidious nature of the smoky poison[9] (cigarettes are its worst form) the cause may often be unsuspected, and so go on, unchecked; and the other, that the progress of growth once interrupted, the gap can never be fully made up. Nature does her best to repair damages and to restore defects, but never goes backwards to remedy neglects. Additional Experiments. Experiment 11. Take a portion of the decalcified bone obtained from Experiment 4, and wash it thoroughly in water: in this it is insoluble. Place it in a solution of carbonate of soda and wash it again. Boil it in water, and from it gelatine will be obtained. Experiment 12. Dissolve in hydrochloric acid a small piece of the powdered bone-ash obtained from Experiment 3. Bubbles of carbon dioxid are given off, indicating the presence of a carbonate. Dilute the solution; add an excess of ammonia, and we find a white precipitate of the phosphate of lime and of magnesia. Experiment 13. Filter the solution in the preceding experiment, and to the filtrate add oxalate of ammonia. The result is a white precipitate of the oxalate of lime, showing there is lime present, but not as a phosphate. Experiment 14. To the solution of mineral matters obtained from Experiment 3, add acetate of soda until free acetic acid is present, recognized by the smell (like dilute vinegar); then add oxalate of ammonia. The result will be a copious white precipitate of lime salts. Experiment 15. _To show how the cancellous structure of bone is able to support a great deal of weight_. Have the market-man saw out a cubic inch from the cancellous tissue of a fresh beef bone and place it on a table with its principal layers upright. Balance a heavy book upon it, and then gradually place upon it various articles and note how many pounds it will support before giving way. Experiment 16. Repeat the last experiment, using a cube of the decalcified bone obtained from Experiment 4.