MILK-BORNE INFECTIONS 431 



teria will be scarce and may be easily overlooked. Negative 

 findings, therefore, do not prove conclusively the absence of dis- 

 ease germs. 



2. Pathogenic bacteria do not multiply readily at the tempera- 

 ture of market milk, while many saprophytes do multiply. Under 

 these conditions isolation of disease germs is difficult. 



3. The time required to isolate pathogenic bacteria from milk 

 is so great that the period of an epidemic is unduly lengthened 

 before preventive measures are put in operation. 



4. The causal organism of some diseases is still undetermined. 



5. Milk may have been intermittently contaminated with the 

 virus of a disease, or only the product of a single day may con- 

 tain the infectious material. At the time the epidemic is dis- 

 covered the milk may be free from dangerous organisms, while 

 the milk actually responsible has been consumed before suspicion 

 pointed to the supply. 



6. Some pathogenic bacteria cannot be cultivated on artificial 

 media. 



However, the menace in milk, great as it is, has probably 

 been somewhat exaggerated, and a beginning at least has been 

 made to cause the pendulum to swing to its normal position. 

 In an interesting article Kelley has shown that the number of 

 cases of disease and deaths due to milk infection is small if com- 

 pared to that due to other causes. In the author's words, "When- 

 ever the subject is approached in an impartial manner it is rather 

 astonishing to see how little real basis there is on which to form 

 any definite estimates as to the comparative importance of milk 

 infection as compared to other modes of infection, such as water, 

 carriers, or direct contact." The author has stated after con- 

 siderable study "that in only 0.03 per cent, of cases was the 

 transmission of diphtheria definitely assigned to infected milk, 

 and in only 0.19 per cent, was milk either proved or suspected; 

 1.6 per cent, of the reported cases of scarlet fever were definitely 

 attributed to milk infection, and 1.8 per cent, proved or suspected; 

 in 79 per cent, of the cases septic sore throat (not reportable in 

 Massachusetts until 1914) milk was assigned as the cause; and 

 in 5 per cent, of the cases of typhoid milk was definitely assigned 

 as the cause, and in 6 per cent, of the cases of typhoid milk was 

 either proved or suspected to be the agent of infection in this 

 disease. Taking all of these diseases in a group, 3.9 per cent, 

 were definitely attributed to milk, and in 4 per cent, of all the 

 cases milk was proved or suspected. Considering mortality, 3 

 per cent, of typhoid deaths are possibly attributable to milk, 

 0.08 per cent, of diphtheria deaths, 0.8 per cent, of scarlet fever 

 deaths, and 98 per cent, of septic sore throat deaths; an average 



