Relation of Disease- Bacteria to Milk. 95 



this way are typhoid fever, diphtheria, scarlet fever and 

 cholera, together with the various illy-defined intestinal 

 troubles of a toxic character that occur in children, es- 

 pecially under the name of cholera infantum, summer 

 complaint, etc. 



Diseases of this class are not derived directly from ani- 

 mals because cattle are not susceptible to the same. 



Modes of infection. In a variety of ways, however, the 

 milk may be subject to contaminating influences after it 

 is drawn from the animal, and so give opportunity for the 

 deyelopment of disease-producing bacteria. The more im- 

 portant methods of infection are as follows: 



1. Infection directly from a pre-existing case of disease on 

 premises. Quite frequently a person in the early stage of 

 a diseased condition may continue at his usual vocation as 

 helper in the barn or dairy, and so give opportunity for 

 direct infection to occur. In the so-called cases of " walk- 

 ing typhoid," this danger is emphasized. Again during 

 the period of convalescence, a similar opportunity exists 

 for direct infection. This method functions more fre- 

 quently in scarlet fever than in typhoid. In some cases 

 infection has been traced to storage of the milk in rooms 

 in the house where it became polluted directly by the 

 emanations of the patient. 1 Among the dwellings of the 

 lower classes where a single room has to be used in com- 

 mon this source of infection has been most frequently ob- 

 served. 



2. Infection through the medium of another person. Not 

 infrequently another individual may serve in the capacity 

 of nurse or attendant to a sick person, and also assist in 

 the handling of the milk, either in milking the animals or 



1 E. Roth, Deutsche Vierteljahresschr. f. oflentl. Gesundheitspfl., 1890, 22:238. 



