5. 'Barnyard milk' is a term used to designate milk taken from unclean animals, or those which have been kept in filthy, unventilated stables. The milk absorbs and carries the odors, which are often plainly perceptible. Such milk may not be poisonous, but it is repulsive.
There is no doubt that milk often serves as the vehicle for the distribution of the germs of various contagious diseases, like scarlet fever, diphtheria, and typhoid fever, from becoming contaminated in some way, either from the hands of milkers or from water used as an adulterant or in cleansing the milk vessels. Recent investigations have also shown that cows are to some extent subject to scarlet fever, the same as human beings, and that milk from infected cows will produce the same disease in the consumer.
Milk should not be kept in brass or copper vessels or in earthen-ware lined with lead glazing; for if the milk becomes acid, it is likely to unite with the metal and form a poisonous compound. Glass and granite ware are better materials in which to keep milk.
Milk should never be allowed to stand uncovered in an occupied room, especially a sitting-room or bedroom, as its dust is likely to contain disease-germs, which falling into the milk, may become a source of serious illness to the consumer. Indeed it is safest to keep milk covered whenever set away, to exclude the germs which are at all times present in the air. A good way is to protect the dishes containing milk with several layers of cheese-cloth, which will permit the air but not the germs to circulate in and out of the pans. Neither should it be allowed to stand where there are strong odors, as it readily takes up by absorption any odors to which it is exposed.
A few years ago Dr. Dougall, of Glasgow, made some very interesting experiments on the absorbent properties of milk. He inclosed in jars a portion of substances giving off emanations, with a uniform quantity of milk, in separate vessels, for a period of eight hours, at the end of which time samples of the milk were drawn off and tested. The result was that milk exposed to the following substances retained odors as described:—
Coal gas, distinct; paraffine oil, strong; turpentine, very strong; onions, very strong; tobacco smoke, very strong; ammonia, moderate; musk, faint; asafetida, distinct; creosote, strong; cheese (stale), distinct; chloroform, moderate; putrid fish, very bad; camphor, moderate; decayed cabbage, distinct.
These facts clearly indicate that if the emanations to which milk is exposed are of a diseased and dangerous quality, it is all but impossible that the milk can remain free from dangerous properties.
Too much pains cannot be taken in the care of milk and vessels containing it. Contact with the smallest quantity of milk which has undergone fermentation will sour the whole; hence the necessity for scrupulous cleanliness of all vessels which have contained milk before they are used again for that purpose.
In washing milk dishes, many persons put them first into scalding water, by which means the albumen in the milk is coagulated; and if there are any crevices or seams in the pans or pails, this coagulated portion is likely to adhere to them like glue, and becoming sour, will form the nucleus for spoiling the next milk put into them. A better way is first to rinse each separately in cold water, not pouring the water from one pan to another, until there is not the slightest milky appearance in the water, then wash in warm suds, or water containing sal-soda, and afterward scald thoroughly; wipe perfectly dry, and place if possible where the sun will have free access to them until they are needed for further use. If sunshine is out of the question, invert the pans or cans over the stove, or place for a few moments in a hot oven.
The treatment of milk varies with its intended use, whether whole or separated from the cream.