252 BACTERIA, YEASTS, AND MOLDS 



Milk. Milk is a means of distributing certain diseases ; 

 not, indeed, a vehicle by which a contagious disease in a 

 household is carried from one member of the family to 

 another, but rather a source by which diseases from out- 

 side may find entrance into the family. The diseases com- 

 monly attributable to milk are not very numerous, five of 

 them being very definite specific diseases and one of a 

 somewhat obscure type. The five definite diseases are 

 tuberculosis, diphtheria, scarlet fever, septic sore throat, 

 and typhoid fever. The other disease referred to is the 

 indefinite series of intestinal troubles known as summer 

 complaint, sum.m,er diarrhoea,' cholera infantum,, etc., all 

 characterized by the presence of diarrhoea and particularly 

 common in warm weather. 



There is no doubt that all of these diseases are occa- 

 sionally distributed by milk. The one most commonly 

 attributed to this source is typhoid fever, and many 

 instances have been recorded where epidemics of typhoid 

 have been due directly to milk contaminated with typhoid- 

 fever bacteria. Epidemics of diphtheria and scarlet fever 

 have also been traced to the same source, though more 

 rarely. The question whether any considerable amount of 

 tuberculosis is attributable to milk has not been settled 

 positively, but the probability seems to be that milk is 

 a source of this disease, especially for young children. 

 Pure milk, however, is never the cause of any of these 

 troubles. Clean milk fresh from a healthy cow is never 

 the source of any of the diseases above mentioned. Some 

 cows have tuberculosis, and the milk of such a cow may be 

 dangerous ; diseased udders are believed to be sometimes 

 the source of the bacteria which cause septic sore throat; 



