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sisting of various sorts of grain, groats, and bread. The guinea pigs did not get the disease when fed upon a one-sided diet consisting of fresh cabbage or fresh potatoes, whereas it was produced by dry potatoes; that is, the disease originates in guinea pigs as well as in man as a result of a diet confined to some special nutriments.

Holst and Frölich also observed that the disease in guinea pigs is favorably influenced by different sorts of nutriments known from human experience as "antiscorbutics." They found, however, that at least one of their nutriments, viz, cabbage, loses a deal but not all its preventive power when boiled for half an hour at 110° C. There is no evidence to show that moderate heating, such as is used in the pasteurization of milk, in any way affects the scorbutic or antiscorbutic qualities of a food.

Infant mortality.—It is now well established that the large majority of infantile deaths is caused by gastro-intestinal diseases. Further, that this great fatality occurs especially among artificially raised infants, and finally that the vast majority of cases and deaths from bowel troubles in children occur during the heated term. The infant mortality in all countries is shockingly high. This is shown to be unnecessary by the fact that infants who are well cared for show a relatively low mortality. Defective feeding is the active cause of this high mortality, while heat, humidity, and bad surroundings are contributary causes. It must be remembered that the normal intestinal mucous membranes are permeable to bacteria, and more so during the period of infantile than of later life. Hence one of the great dangers of using bacteria-laden milk. While the factors involved in this “slaughter of the innocents" are numerous, primarily or secondarily they depend upon the activity of micro-organisms. Freeman believes that the decline in the infant mortality in the United States during the last ten years, and especially in New York City, is due for the most part to the decline in mortality from summer diarrhea, and states "that the general adoption of pasteurized and sterilized milk for infant feeding is by far the most important agency." A definite example of the diminution in mortality from pasteurizing the milk occurred in the infants' hospital at Randall's Island, where the mortality in 1897, with raw milk, was 44.36 per cent, while in 1898, with pasteurization of the milk, it was 19.80 per cent.

Numerous similar instances of the beneficial effect upon infant mortality and morbidity are found in the literature.

A reduction in the infant mortality may be accomplished without the heating of the milk. This has been shown by Doctor Goler, who conducted an aggressive campaign to improve the milk supply for

a Freeman, Roland G.: Medical News, September 5, 1905.

infant feeding in Rochester, N. Y. His methods consisted mainly in education in the nursery and on the dairy farm. The clean milk obtained thus and distributed through milk depots resulted in lowering the death rate in children under 5 years from 33 per cent from all causes to 20 per cent, and now (1907) it is 15 per cent.

a

Park and Holt studied groups of infants in the tenement houses and institutions in New York for periods of about three months in the summers of two years (1902-3). This work is the most important evidence we have on the subject, for it combines careful clinical observation with laboratory studies. Although the number of cases was comparatively small, the results obtained were almost identical during the two summers, and indicate that even fairly pure milk, when given raw in hot weather, causes illness in a much larger percentage of cases than the same milk given after pasteurization. A considerable percentage of infants. however, did apparently as well on raw as on pasteurized milk. Park and Holt conclude in part:

The number of bacteria which may accumulate before milk becomes noticeably harmful to the average infant in summer differs with the nature of the bacteria present, the age of the milk, and the temperature at which it has been kept. When milk is taken raw the fewer bacteria present the better are the results. Of the usual varieties, over 1,000,000 bacteria per cubic centimeter are certainly deleterious to the average infant. However, many infants take such milk without apparently harmful results. Heat above 170° F.

(77° C.) not only destroys most of the bacteria present, but apparently some of their poisonous products. No harm from the bacteria previously existing in recently heated milk was noticed in these observations, unless they had amounted to many millions, but in such numbers they were decidedly deleterious.

When milk of average quality was fed sterilized and raw, those infants who received milk previously heated did on the average much better in warm weather than those who received it raw. The difference was so quickly manifest and so marked that there could be no mistaking the meaning of the results.

A few cases of acute indigestion were seen immediately following the use of pasteurized milk more than thirty-six hours old. Samples of such milk were found to contain more than 100,000,000 bacteria per cubic centimeter. mostly spore-bearing varieties. The deleterious effects, though striking, were not serious or lasting.

After the first twelve months of life, infants are less and less affected by the bacteria in milk derived from healthy cattle. According to these observations, when the milk had been kept cool the bacteria did not appear to injure the children over three years of age at any season of the year, unless in very great

excess.

❝ Park, Wm. H., and Holt, L. Emmett: Report upon the results with different kinds of pure and impure milk in infant feeding in tenement houses and institutions of New York City. A clinical and bacteriological study. Medical News, Vol. 83, 1903, p. 1066.

The general practice of heating milk, which has now become a custom among the tenement population of New York, is undoubtedly a large factor in the lessened infant mortality during the hot months.

Only the purest milk should be taken raw, especially in summer.

No discussion of the subject is complete without recognition of the debt the world owes Mr. Nathan Straus for his early and persistent advocacy of pasteurization and the establishment of his infants' milk depots. Through his influence and philanthropy this movement has now spread to many cities of this country and abroad.

HOME PASTEURIZATION.

If pasteurization is to be done perhaps the best place to do it is in the home, but the heating of milk to just 60° and the holding of it to just that temperature for twenty minutes, then cooling it rapidly, requires intelligence and careful manipulation. With the possible exception of infant feeding, it would perhaps be better and cheaper to pasteurize the milk in bulk under competent supervision instead of leaving it to the usual carelessness of cooks, who can not be expected to master the technic nor appreciate the difficulties. Imperfect pasteurization may be worse than none, for it may result only in further contamination of the milk.

Milk pasteurized in the home is commonly heated too high and not rapidly cooled.

The most practical home pasteurizer is that devised by Freeman." The following experiments, made in the Hygiene Laboratory, with Freeman's pasteurizer show its efficiency:

Test No, A with Freeman's pasteurizer.

Temperature of milk, 9° C.

Temperature of water in jacket, 25° C.

Milk introduced into boiling water and removed from the fire.

Milk temperature—

Five minutes after immersion in boiling water..
Ten minutes after immersion in boiling water.
Fifteen minutes after immersion in boiling water.
Twenty minutes after immersion in boiling water.
Twenty-five minutes after immersion in boiling water.

Twenty-eight minutes after immersion in boiling water.

Whole time, twenty-eight minutes.

Above 67° C. for thirteen minutes.

° C.

47.5

63

67.4

68.8

68.9

68.9

Took fifteen minutes in running tap water at 22° C. to cool milk to 30° C.

Freeman, Rowland G.: Low temperature pasteurization of milk at about 68° C. (155° F.). Arch. of ped., vol. - 1896, p.-.

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Five minutes after immersion in boiling water.
Ten minutes after impression in boiling water.
Fifteen minutes after immersion in boiling water.
Twenty minutes after immersion in boiling water.
Twenty-five minutes after immersion in boiling water-
Thirty minutes after immersion in boiling water---.
Thirty-five minutes after immersion in boiling water_
Forty minutes after immersion in boiling water..
Forty-five minutes after immersion in boiling water-

°C.

50

63

66. 6

67.5

67.7

67.4

67 66.6

66

It took thirteen minutes in running tap water, at 22° C., to cool the milk to 30° C.

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a Colonies on agar plates after 24 hours' incubation at 37° C.

NOTE. Recently (November, 1907) Freeman has modified his pasteurizer so that the milk is heated to 60° C. for 40 minutes. (See his article on "The ferments in milk and their relation to pasteurization,” in the Jour. of the Amer. Med. Assn., Nov. 23, 1907, Vol. XLIX, No. 21, p. 1740.)

Milk is frequently pasteurized by simply placing the bottle of milk as it is received, in a pot of water, the water boiled for a variable length of time, and then cooled. As will be shown by the following experiments, this is not always an entirely safe procedure for the purposes of home pasteurization. The depth of water in which the bottle is immersed markedly affects the results. The neck of the bottle must always project above the water, and unless the pot has a lid the upper layers of the milk may escape heating, especially if the contents have not been well shaken up and the thick cream, which is in part turned to butter as a result of agitation on the delivery wagon, prevents circulation of the fluid.

It will be seen in some of the experiments made by myself in the Hygienic Laboratory that contrary to what might be expected from the physics of fluids, the top layers of the milk are sometimes not as hot as the bottom or require a much longer time to heat up.

Pint mixed market milk.

EXPERIMENT No. 1.

Bottle immersed in water to its lip.

Distinct cream line from standing over six hours before heating; thick cream, almost butter, floating on top.

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