704 BACTERIA IN AIR, SOIL, WATER, AND MILK 



water, one hundred and ten to milk, and seventy-eight to all other 

 causes. 



Trask ^ compiled statistics of one hundred and seventy-nine typhoid 

 epidemics supposed to have been caused by milk, in various parts of the 

 world. In all such epidemics the origin of infection was generally trace- 

 able to diseased or convalescent persons employed in dairies, to con- 

 taminated well water used in washing milk utensils, or to the use of cans 

 and bottles returned from dwellings where typhoid fever had existed. 

 Actual bacteriological proof of the infectiousness of milk by the isolation 

 of Bacillus typhosus is rare, but has been accomplished in isolated in- 

 stances. In the case of one epidemic, Conradi ^ isolated the bacillus from 

 the milk on sale at a bakery at which a large number of the infected 

 individuals had purchased their milk. The examination of market milk 

 at Chicago, through a period of eight years, revealed the presence of 

 typhoid bacilli but three times. 



In spite of the few cases in which actual bacteriological proof has been 

 brought, it is not unlikely that careful and systematic researches would 

 reveal a far greater number, since many writers have shown that typhoid 

 bacilli may remain alive in raw milk for as long as thirty days,' and 

 may actively proliferate in the milk during this time. One peculiarity 

 of epidemics which may aid in arousing the suspicion that they have 

 originated in milk is that, in such cases, women and children are far 

 more frequently attacked than men.^ 



A feature which adds considerably to the dangers of milk infection 

 is the unfortunate absence of any gross changes, such as coagulation, 

 by the growth of typhoid bacilli. 



Scarlet fever,^ though as yet of unknown etiology, has in many cases 

 been traced indirectly to milk infection. Trask has collected fifty-one 

 epidemics of scarlet fever presumably due to milk. In one epidemic 

 occurring in Norwalk, Conn.,' twenty-nine cases were distributed among 

 twenty-five families living in twenty-four different houses. The indi- 

 viduals affected did not attend the same school, and were of entirely 

 different social standing, the only factor common to all of them being 

 the milk supply. 



1 Trask, Bull. No. 41, U. S. Pub. Health and Mar. Hosp. Serv., Wash. 



2 Conradi, Cent. f. Bakt., I, xl, 1905. 



3 Heim, Arb. a. d. kais. Gesundheitsamt, v. 

 •> Wilckens, Zeit. f. Hyg., xxvii, 1898. 



6 Trask, loc. cit. 



» Herbert E. Smith, Rep. Conn. State Bd. of Health, 1897. 



