412 THE BACTERIAL ASPECTS OF PASTEURIZATION 



of the udder, which occurs in from i to 2 per cent of all tuberculous cows, or indi- 

 rectly through cow manure. In the latter case the tubercle bacilli are coughed up, 

 swallowed, and passed in the feces. Practically all market milk contains cow feces. 

 Tuberculosis in cattle is very prevalent. In Holland nearly one-tenth of all cattle 

 killed for food are tuberculous; in Berlin, 16 per cent; in Saxony, 30 per cent; in 

 Pennsylvania, from 2 to 3 per cent. The "milk" from a tuberculous udder, when ex- 

 amined under the microscope, may contain as many tubercle bacilli as are ordinarily 

 found in tuberculous sputum. The milk from a tuberculous udder of one cow may 

 contain sufhcient bacilli seriously to infect the mixed milk of twenty-five or thirty 

 cows. In one case Ostertag found that o.ooi cc. of the secretion from a tuberculous 

 udder was sufficient to cause tuberculosis in a guinea pig. In such a case a child 

 would receive myriads in a gill. 



We have evidence from four typical American cities. A total of 551 samples of 

 raw milk have been examined in which tubercle bacilli were found in 46, making a 

 percentage of 8.3. Tonney, in Chicago (1910), found 10.5 per cent positive; Hess, 

 in New York (1909), found 16 per cent positive; Anderson in Washington, found 6.72 

 per cent; and Goler, in Rochester, found 5 per cent of samples examined to contain 

 tubercle bacilli. This may be taken as representative for the entire country. 



Wherever these investigations have been carried out similar and sometimes higher 

 results have been obtained, both in Europe and in this country. It is believed that 

 the figures are an underestimate, for the methods used in the laboratory are not suffi- 

 ciently delicate to detect a few tubercle bacilli in milk. Unless these micro-organisms 

 are present in considerable numbers, they are likely to escape detection, for the tests 

 depend upon infecting guinea pigs. Ordinary cultural or microscopic methods are 

 not satisfactory to disclose the presence of tubercle bacilli in milk. In any event, it 

 is clear that the common, raw, market milk furnished all large cities and probably 

 most small towns very often contains tubercle bacilli. The hazard is real/ 



Typhoid fever. — Of milk-borne epidemics, typhoid fever takes the lead. Typhoid 

 bacilli may swarm in milk without appreciably altering its taste, odor, or appearance. 

 In our Washington studies, 10 per cent of all the cases of typhoid fever during the 

 four years 1907-10 were traced to milk. The recent figures for Massachusetts are 

 given in Table I. Note that despite the decrease in the number of cases from year 

 to year, the percentage of cases due to infected milk remains about the same. An 

 outbreak of typhoid fever of unusual magnitude, in fact the largest on record, oc- 

 curred in Montreal, Canada; between March i and June 29, 1927, there were 4,755 

 cases with 453 deaths.^ All outbreaks occur on raw-milk supplies. The milk usually 

 becomes infected by a carrier, sometimes by a convalescent or a missed case, and 

 occasionally indirectly through infected water, utensils, etc. 



Bolduan estimated in 191 2 that from 300 to 400 cases of typhoid fever each yeaf 

 come in contact with the milk supplied New York City. He further stated that "the 

 startling total of 90 to 120 typhoid carriers now probably menace the supply of this 

 city." This estimate is based upon the fact that about 200,000 persons come into 



' Cf. Tonney, F. O., White, J. L., and Danforth, T. F.: ibid., 17, 491. 1927. 

 ^Report of the U. S. Public Health Service on the Montreal Typhoid Fever Situation. U. S. Pub. 

 Health Rep., 42, 1893. 1927. 



