ACIDITY
Like mother's milk, the cow's milk is neutral as it comes from the udder; but, on standing, it quickly changes, soon becoming slightly acid, as shown by testing with blue litmus paper. In fact, what is known as ordinarily fresh milk, if subjected to the litmus paper test, always gives an acid reaction. This acidity is neutralized by adding lime water to the formula in the proportion of one ounce to each twenty-ounce mixture. Ordinary baking soda is sometimes prescribed by physicians in place of the lime water. In the event of obstinate constipation, milk of magnesia is sometimes added to the day's feedings.
CREAM
There may be procured in any large city an instrument called the cream gauge, which registers approximately (not accurately) the richness of milk. Some milk, even though rich, parts with its cream very slowly; while some poor milk allows nearly all the cream quickly to rise to the surface. We know of no way for the mother to determine the amount of cream (without the cream gauge) except by the color and richness of the milk. In cities it is very convenient to send a specimen of the milk to the laboratories to be examined by experts, who will gladly render a report to both physician and mother.
Fig. 11. A Sanitary Dairy.
The lactometer is a little instrument used to estimate the specific gravity of milk. An ordinary urinometer such as used by physicians in estimating the specific gravity of urine may also be used. The specific gravity of cow's milk should not register below 1028 or above 1033.
HERD MILK
Milk from a single cow is not to be desired for baby's food because of its liability to vary from day to day, not to mention the danger of the cow's becoming sick. Authorities have agreed that herd milk of Holstein or ordinary grade cows is best for infant feeding. This mixed-herd milk contains just about the proper percentage of fat; whereas, if Jersey milk must be used, some of the cream should be taken away. Our milk should come from healthy cows which have been tested for tuberculosis at least every three months.