If the milk is kept in a cold place the bacteria multiply slowly. If it is kept in a warm place they increase in numbers at a rate that is marvelous, and consequently the milk sours much sooner. Even if the milk is kept cold, bacterial growth will soon take place, but it will perhaps not be lactic acid bacteria. It may be a form that causes the milk to become ropy and slimy or one that gives it a bad odor.
Bacteria are like other forms of vegetation, such as grass, weeds, flowers and trees, in that some flourish best under one condition and others under dissimilar conditions, and they struggle one against the other for subsistence and existence. Like flowers there are thousands of different forms of bacteria and they vary according to their food and environment.
Peculiar odors in milk generally come from certain kinds of food given to the cows, such as turnips; from bacterial action; or from flavors absorbed from other foods or from odors in the air. Milk should not be exposed to odorous substances, for it becomes tainted very quickly. Sometimes yeast finds its way into milk and causes decomposition of the sugar with the formation of carbon dioxide and alcohol.
A count of the bacteria in milk often serves a good purpose, for it shows whether it is good and has had proper care. The consumers have a right to demand milk low in bacteria, for if no preservatives have been used, that means clean milk. If we could live in our pristine state of beatific bliss, if such it was, we would not have to use milk after childhood is past, but our present condition demands the use of easily digested foods and to many milk is almost a necessity.
The milk in the udder of a healthy cow is almost surely free from bacteria, but the moment it is exposed to the air these little beings start to drop into the fluid.
The bacterial standards given by various city health departments vary. Those who are mathematically inclined may find the following figures interesting: In some great cities they allow 500,000 bacteria to the cubic centimeter of milk. A cubic centimeter contains about twenty-five drops. In other words, they allow 20,000 bacteria per drop. This may seem very lively milk, but these bacteria are so small that about 25,000 of them laid end to end measure only about an inch, and it would take 17,000,000,000,000 of them to weigh an ounce, according to estimates. These are the tiny vegetables we hear and read so much about, that we are warned against and fear so much. Truly the pygmies are having their innings and making cowards of men. The bacteria multiply by the simple process of growing longer and splitting into two, fission, as it is called, and the process is so rapid that within an hour or two after being formed a bacterium may be raising a family of its own.
Some of the milk brought to the cities contains as many as 15,000,000 bacteria per cubic centimeter, that is, about 600,000 per drop. This milk is either very filthy or it has been poorly cared for and should not be given to babies and young children. The filthiest milk may contain several billion bacteria to the cubic centimeter.
By using care milk containing but 100, or even fewer, bacteria per drop can be produced. From the standpoint of cleanliness this is excellent milk. Of course, the dairyman who takes pride enough in his work to produce such milk will sell nothing but what is first-class, and if he has business acumen he can always get more than the market price for his product.
The talk about germs has been overdone, but no one can deny that the study of bacteriology has made people more careful about foods. The filthy dairies that were the rule a few years ago are slowly being replaced by dairies that are comfortable, well lighted and clean. Do not allow the germs to scare you, for if ordinary precautions are taken no more of them will be present than are necessary, and they are necessary. They thrive best in filth, and they are dangerous only to those who live so that they have no resistance.
Wholesome milk can be produced only by healthy animals. Bovine health can be secured by the same means as human health. The cows must be properly fed and housed. They must have both ventilation and light. They must not be unduly worried. If a nursing of an angry mother's milk is at times poisonous enough to kill a baby, you may be sure that the milk from an abused, irritated and angry cow is also injurious. If the animals are kept comfortable and happy they will do the best producing, both in quality and quantity. It may sound far-fetched to some to advocate keeping animals happy in order to get them to produce much and give quality products, but it is good science and good sense. Happy cows give more and better milk than the mistreated ones. The singing hens are the best layers.