When obliged to buy the ordinary milk of commerce, select if possible that which is put up in glass jars. There are farmers who do this. Each jar is sealed, marked with the owner's name and address, and the date of sending. Such milk does not become contaminated with bad air in transit, cannot be tampered with by middlemen, and must be free from dirt, as it would show through the glass; each customer gets exactly a quart, with all the cream that belongs to it; moreover, the owner, having attached his name, has thus put his reputation at stake, and is not likely to sell inferior milk. When this is not practicable, search for the best and cleanest dairy, and see that the milk is delivered as soon as possible after being received at the dairy. Milk should not be bought from small stores. The best milk comes from cows that have good pasturage, with clean running water, and that are fed in winter on dry fodder and grain, and not on ensilage and brewery waste. According to the reports of the American Public Health Association, _one fifth_ of all the deaths among infants may be traced to the milk supply, and there is no doubt that most of the sickness of bottle-fed children, during the summer months, is directly due to the unhealthy condition of their food. It then becomes the imperative duty of every mother, nurse, or other person who has the care of children, to learn, if she does not already know, the simpler tests for milk, and something of the philosophy of the feeding of her charge.[53] When such knowledge is more general, and women are able to determine intelligently the quality of the milk which is offered them, then will milk-dealers be forced to cease mixing, adulterating, and otherwise tampering with the milk, which, as a general thing, is sold at the farms in excellent condition. The first object is to secure a good quality of milk; then comes the consideration of how it shall be prepared: this must be in such manner as shall render it as nearly like human milk, in composition and digestibility, as possible. Comparison of the tables just given shows that cow's milk contains more nitrogenous matter and salts, and less sugar, than human milk.[54] By diluting with water to reduce the protein and salts, and adding sugar and a little cream, the proportions of these different substances may be made to approximate those in mother's milk. In both the sugar is the same--lactose, or milk-sugar; the fats are also much alike in each; but the albuminous matter of cow's milk differs somewhat from that of human milk, particularly in the way in which it coagulates in the presence of acids. Human milk forms into small, light, feathery curds; cow's milk into large, compact, not so easily digested masses. It is necessary, therefore, to seek the means for preventing the coagulation of milk in large curds in the stomach of the child--in other words, to so treat cow's milk that it shall coagulate more like human milk. This may be done in two ways: