For the disinfection of walls in stables and barns, common thin _white wash_ Ca(OH)_{2} is admirably adapted if made from freshly-burned quick lime. It possesses strong germicidal powers, increases the amount of light in the barn, is a good absorbent of odors, and is exceedingly cheap.

Carbolic acid, creosote, and such products, while excellent disinfectants, cannot well be used on account of their odor, especially in factories.

For gutters, drains, and waste pipes in factories, _vitriol salts_ (sulfates of copper, iron and zinc) are sometimes used. These are deodorants as well as disinfectants, and are not so objectionable to use on account of their odor.

These suggestions as to the use of chemicals, however, only apply to extreme cases and should not be brought into requisition until a thorough application of hot water, soap, a little soda, and the scrubbing brush have failed to do their work.

FOOTNOTES:

[51] Gunther and Thierfelder, Arch. f. Hyg., 25:164, 1895; Leichmann, Cent. f. Bakt., 2:281, 1896; Esten, 9 Rept. Storrs Expt. Stat., p. 44, 1896; Dinwiddie, Bull. 45, Ark. Expt. Stat., May, 1897; Kozai, Zeit. f.

Hyg., 38:386, 1901; Weigmann, Hyg. Milk Congress, Hamburg, 1903, p. 375.

[52] McDonnell, Inaug. Diss., Kiel. 1899, p. 39.

[53] Kayser, Cent. f. Bakt. II. Abt. 1:436.

[54] Treadwell, Science, 1894, 17:178.

[55] Conn, 5 Rept. Storrs Expt. Stat., 1892, p. 396.

[56] Fermi, Arch. f. Hyg., 1892, 14:1.

[57] Duclaux, Le Lait, p. 121.

[58] Duclaux, Principes de Laiterie, p. 67.

[59] Guillebeau (Milch Zeit., 1892, p. 808) has studied over a dozen different forms that possess this property.

[60] Ward, Bull. 165, Cornell Expt. Stat., Mch., 1899; also Bull. 195, Ibid., Nov., 1901.

[61] Adametz, Landw. Jahr., 1891, p. 185.

[62] Marshall, Mich. Expt. Stat., Bull. 140.

[63] Milch Zeit., 1899, p. 982.

[64] Duclaux, Principes de Laiterie, p. 60. Heinze and Cohn, Zeit. f.

Hyg., 46: 286, 1904.

[65] Bull. 128, Wis. Expt. Stat., Sept. 1905.

[66] Freudenreich, Landw. Jahr. d. Schweiz, 1896, 10; 1.

[67] Weigmann, Milch Zeit., 1890, p. 881.

[68] Conn, 3 Rept. Storrs Expt. Stat., 1890, p. 158.

[69] Freudenreich, Fuhl. Landw. Ztg. 43: 361.

[70] Harrison, Bull. 120 Ont. Agr'l. Coll., May, 1902.

[71] Milch Zeit. 22:569.

[72] Marshall, Bull. 146, Mich. Expt. Stat., p. 16.

[73] Grotenfelt, Milch Zeit., 1889, p. 263.

[74] Menge, Cent. f. Bakt., 6:596; Keferstein, Cent. f. Bakt., 21:177.

[75] Heim, Arb. a. d. Kais. Gesundheitsamte, 5:578.

[76] Adametz, Milch Zeit., 1890, p. 225.

[77] 12 Rept. Wis. Expt. Stat., 1895, p. 148; also Bull. 67, Ibid., June, 1898.

CHAPTER V.

RELATION OF DISEASE-BACTERIA TO MILK.

Practical experience with epidemic disease has abundantly demonstrated the fact that milk not infrequently serves as a vehicle for the dissemination of contagion. Attention has been prominently called to this relation by Ernest Hart,[78] who in 1880 compiled statistical evidence showing the numerous outbreaks of various contagious diseases that had been a.s.sociated with milk infection up to that time. Since then, further compilations have been made by Freeman,[79] and also by Busey and Kober,[80] who have collected the data with reference to outbreaks from 1880 to 1899.

These statistics indicate the relative importance of milk as a factor in the dissemination of disease.

The danger from this source is much intensified for the reason that milk, generally speaking, is consumed in a raw state; and also because a considerable number of disease-producing bacteria are able, not merely to exist, but actually thrive and grow in milk, even though the normal milk bacteria are also present. Moreover the recognition of the presence of such pathogenic forms is complicated by the fact that often they do not alter the appearance of the milk sufficiently so that their presence can be detected by a physical examination. These facts which have been experimentally determined, coupled with the numerous clinical cases on record, make a strong case against milk serving as an agent in the dissemination of disease.

~Origin of pathogenic bacteria in milk.~ Disease-producing bacteria may be grouped with reference to their relation toward milk into two cla.s.ses, depending upon the manner in which infection occurs:

Cla.s.s I. Disease-producing bacteria capable of being transmitted directly from a diseased animal to man through the medium of infected milk.

Cla.s.s II. Bacteria pathogenic for man but not for cattle which are capable of thriving in milk after it is drawn from the animal.

In the first group the disease produced by the specific organism must be common to both cattle and man. The organism must live a parasitic life in the animal, developing in the udder, and so infect the milk supply.

It may, of course, happen that diseases toward which domestic animals alone are susceptible may be spread from one animal to another in this way without affecting human beings.

In the second group, the bacterial species lives a saprophytic existence, growing in milk, if it happens to find its way therein. In such cases milk indirectly serves as an agent in the dissemination of disease, by giving conditions favorable to the growth of the disease germ.

By far the most important of diseases that may be transmitted directly from animal to man through a diseased milk supply is tuberculosis, but in addition to this, foot and mouth disease (aphthous fever in children), anthrax and acute enteric troubles have also been traced to a similar source of infection.

The most important specific diseases that have been disseminated through subsequent pollution of the milk are typhoid fever, diphtheria, scarlet fever and cholera, but, of course, the possibility exists that any disease germ capable of living and thriving in milk may be spread in this way. In addition to these diseases that are caused by the introduction of specific organisms (the causal organism of scarlet fever has not yet been definitely determined), there are a large number of more or less illy-defined troubles of an intestinal character that occur especially in infants and young children that are undoubtedly attributable to the activity of microorganisms that gain access to milk during and subsequent to the milking, and which produce changes in milk before or after its ingestion that result in the formation of toxic products.

DISEASES TRANSMISSIBLE FROM ANIMAL TO MAN THROUGH DISEASED MILK.

~Tuberculosis.~ In view of the wide-spread distribution of this disease in both the human and the bovine race, the relation of the same to milk supplies is a question of great importance. It is now generally admitted that the different types of tubercular disease found in different kinds of animals and man are attributable to the development of the same organism, _Bacillus tuberculosis_, although there are varieties of this organism found in different species of animals that are sufficiently distinct to permit of recognition.