Rural Hygiene

by Henry N. Ogden

Tuberculosis.

So far as tuberculosis is concerned, nothing seems to be definitely proved. There is little fear of milk becoming infected from tuberculous patients or of the disease being transmitted through milk from one person to another, as with the three other diseases mentioned. The possibility of infection here lies in the fact that a cow, like man, is susceptible to tuberculosis as a disease, and undergoes the same course of prolonged suffering and death. The interesting question is whether the disease may be transmitted from a cow to a man through the cow's milk. With all the refinements suggested by science as to the virulence of the disease thus transmitted, with a study of the comparative symptoms of the two diseases, of the progress of the disease in the cow when the germs are found in the milk, and of the possibility of eliminating these germs by heating or otherwise, the danger from diseased cows is still unsettled.

So far as present knowledge goes, it is probably conservative to say that although tests made on cows by inoculation with tuberculin show that a large proportion of the animals in the various dairy herds are more or less affected by tuberculosis, yet only a small proportion of the milk from such cows shows the presence of the tuberculosis bacillus. So far as statistics can be given on this subject, it seems probable that not more than ten per cent of the cows reacting under the tuberculin test would show tubercular bacilli in the milk, or would develop tubercular reactions if the milk were used in inoculations. The reason for this is probably that the tubercular growth in the cow does not naturally attack the milk glands until the disease is well advanced, and when the general appearance of the cow indicates severe illness, so that any careful milkman would not use the particular milk, even if the milk flow did not cease. It is not reasonable to assume that all milk from tubercular cows is itself infected, nor yet that all children drinking milk so infected will contract the disease. But the mere possibility of demonstrating that a small percentage of tubercular cows will cause human tuberculosis is sufficient to justify all possible precautions against tubercular animals and against the distribution of tubercular milk. In this connection it is worth while noting that the cows most affected by tuberculosis are those confined in small crowded stables, with no fresh air, with no exercise, and with insufficient or improper food. Unfortunately it is not possible to trace the connection between the particular animal responsible for the disease in a human being, since the period required for the development of the disease is so great that the possible time of onset is forgotten and the cause of the disease entirely out of mind.

It can only be said, therefore, that laboratory experiments have demonstrated the presence of the tuberculosis bacillus in milk from tubercular cows, and that this bacillus is known to produce tubercular lesions in man. It is wise, therefore, to eliminate the milk of tubercular cows if healthy milk is to be provided.

Methods of obtaining clean milk.

Aside from the infection of milk by specific disease-producing bacteria, the milkman of to-day must be very careful to avoid a milk which shall contain large numbers of bacteria of any type which, while not producing any specific disease, nevertheless causes changes in the chemical composition of the milk, which make it at the same time unfit as an article of food for individuals and shows the possibility of other kinds of infection.

There are two axioms to be followed if good clean milk is to be produced, and those are that the milking and straining shall be done in clean stables, from clean cows, by clean persons; and the other that the milk shall be cooled to a temperature of fifty degrees or less as soon as received from the cow. Neither of these requirements is difficult to attain, but they constitute the sole reason why some milk contains a million or more bacteria and other milk less than a thousand; and it is quite possible by enforcing these two requirements to change the number of bacteria in milk from the large figure to the small one.

Probably it is in the stable where the cows are milked that the most important factor in producing large numbers of bacteria is to be found. Not long ago the writer saw a number of stables, the ceilings of which were poles on which the winter supply of hay was stored and the atmosphere was noticeably dust-laden. A good milk could not be furnished from such a stable, and therefore it may be set down as the first requirement that the ceiling of the stable should be entirely dust-tight. Some of the best stables in the country for this reason have no loft of any sort above the cattle, but if the ceiling is tight,—that is, made with tongue-and-groove boards and then painted,—there can be no objection to the storage of hay in the loft. Hay should not be taken from the loft or fed to the cows just before milking, because the very moving of a forkful of hay through the air of the stable stirs up so large a number of bacteria in the air that quantities of them will later fall into the milk-pail.

Light and air in a stable are both important, not so much for the quality of the milk as for the health of the cows that furnish the milk. Ventilation and sunlight are both excellent antiseptics. The ordinary rule for the amount of window area per cow as given by the United States Department of Agriculture is four square feet of window surface. But it is not easy to definitely state any fixed amount of window area, since the value of the window is in its disinfecting power on the bacterial life of the stable, and this is greater or less as the windows receive the direct sunlight or are hidden under eaves where no sunlight reaches them.

The next factor in the production of good milk is the condition of the walls of the stable. Like the ceiling, they should be absolutely free from dust, and should be smooth, so that they may be brushed or even washed clean. For this reason, walls with ledges are objectionable, and all horizontal surfaces in a stable are undesirable. Tongue-and-groove sheeting should never be laid horizontally, but rather vertically, and a smooth brick or concrete wall is better than wood in any case. The same care must be taken to have the floor clean and dry. A floor of saturated wood, containing millions of bacteria which are stirred up by the milker moving around, causes many of those millions to be deposited in the milk-pail. A concrete floor for the stalls and drains is the ideal construction, and both should be thoroughly cleaned morning and night, so that no dried refuse may remain as the living place for bacteria. Nor should the manure thrown from the stalls be left in the vicinity of the barn, but carried away at least 200 feet, in order that the barnyard may be kept dry and clean, that no smell from the manure may reach the milk, and that the flies which come from manure piles may be kept at least that distance from the cows.