=Action of the Heart.=--The alternate contraction and dilation of the muscles of the heart constitute the heart-beats or throbs of the pulse. These vary with the individual. In the average adult, the number of beats is seventy-two per minute. In the cases of Bonaparte and Wellington the number was less than fifty. Heat, food, and exercise increase its action, as cold, fasting, and sleep diminish it. Emotion of joy, grief, and fear also exert a modifying influence. It is a matter of wonder how the silent forces within a tree can lift from the soil, through its minute pipes, and extract from the air, through the small pores of the leaves, the many tons of material that go to make up the giant of the forest. The tons of physical energy bound up in that small organ, the human heart, is a matter no less marvelous. Estimating the amount of blood expelled by each contraction of the ventricles of the heart at four ounces, we have a total of twelve tons a day, or over four thousand tons in a year. =Assimilation.=--The crowning act in the conversion of lifeless food into living tissue takes place in the meshes of the capillary network, and is called assimilation. This process is alike mysterious and wonderful. By a peculiar power of selection, each bone and muscle and tissue appropriates that portion of the blood which it needs for its own development or for the repair of the waste, and applies it in such a manner as to preserve the form and size and strength of the part, ever maintaining a proper balance of the two sides of the body, unless thwarted in its operation by some act of the individual. =Adulteration of Food Products.=--National, State, and Municipal Boards of Health, and food inspectors may do much to preserve health, but when they have done all that it is possible for them to do, much will still remain for the individual. With the products of the world exposed for sale in our markets, with the advertising pages of our magazines and newspapers filled with irresistible arguments in favor of some newly-discovered breakfast food or new preparation of canned goods, the need of individual knowledge and caution daily increases. There is cause for congratulation in the fact that those articles which constitute the larger portion of our food are but little adulterated. In the States that impose legal penalties the proportion of adulterated products is quite low. The value of a stringent law is seen in the decrease of the adulteration of cream of tartar, which, in Massachusetts, fell from forty-two per cent in samples examined in 1879, to five per cent in 1898. Spices, flavoring extracts, and canned goods afford the most promising field for adulteration.