which they are subject. This volume is intended to substitute knowledge for speculation, and to give the dairyman data whereby he can best utilize his products.
There is a preliminary introduction on bacteria and their relation to dairying, so plainly written that all may comprehend it. With this information as a basis, the author proceeds to consider milk as it is drawn from the udder—properly sterile—and describes the sources of infection in the stable and their prevention. He calls attention to the danger of pouring abnormal milk on the stable floor or of feeding it to swine. Both in Germany and Denmark swine fed on centrifuge milk slime have been found tuberculous.
The author states that milk from tuberculous cows should not be used without being freed from its infectious qualities. This is unfortunate, for there is no certain and safe method of disinfecting such milk, and Prudden's experiments have shown that the sterilized products of tubercle bacilli will produce organic lesions that are severe and permanent. Such milk should never be used for any purpose, and the cow should be killed.
We are glad to note the author's emphasis on better lighting of cow-stables; he might have cited the fact that bright light is inimical to the best growth of microorganisms. Hesse's experiments, here cited, that in the air of a cow-stable there were one hundred and twenty bacteria and molds while in that of an occupied schoolroom there were only eighty micro-organisms to the litre, only evidences the bad ventilation of each of those places.
In the section on cooling milk he refers to the value of ice to the dairyman, though it is in a subsequent chapter that he calls attention to the fact that the ice should not come in contact with the milk, because ice may contain pathogenic micro-organisms.
It would seem that the objection to the use of soda in cleansing milk-vessels is not well founded. In surgical and other disinfection alkaline water is of value in securing an aseptic condition, and its employment in the cleaning of these vessels seems to us particularly appropriate, though, of course, the vessel should be subsequently scalded with boiling water. A thorough steaming of these vessels is one of the best procedures that can be employed.
The annual cleaning of the stable is a hygienic necessity, and the means of disinfection herein indicated are easily applied.
The difference in the number of bacteria in one cubic centimetre of milk that has been obtained in a pasture and in a barn is striking:
Knopf has found from 60,000 to 100,000 bacteria in one cubic centimetre of recently drawn milk, and the author found in milk from a filthy stable from 670,000 to 780,000 bacteria per cubic centimetre. The investigations made by Sedgwick and Batchelder in Boston showed that milk sold in that city contained from 1,438,000 to 4,577,000 bacteria per cubic centimetre. The author gives a useful review of the various microorganisms found in milk, and calls attention to the fact that the kinds are more important than the number of organisms.
Due importance is attached to the cleanliness of employees in butter and cheese factories, to their clothing and the cleanness of their hands.
The chapter on milk for city consumption is well written, but State dairy inspectors will have to be much further removed from political influences than they are at present before milk supplied to cities will cease to be a fertile source of causation of tuberculosis.
There is no doubt that properly condensed unsweetened milk is one of the best articles that can be used as a milk foodstuff, because it may be diluted with water as necessary, and it does not contain the pus and blood corpuscles, hair, and manure particles that are in any milk sterilized by heating. Filtration sterilization has not proved practical. A chapter is devoted to milk pasteurization, which the researches of Freeman and others have shown to be so much more satisfactory than sterilization by heating.
The advantages of the centrifugal method for cream separation and pasteurization of cream receive due consideration.
The manufacture and handling of butter