200 AGRICUI.TURE OF MAINE. 



3. TRANSMISSION OF DISEASES PECUEIAR TO MAN THROUGH 

 ACCIDENTAL INFECTION OF MILK. 



Another way in which milk produces diseases in man is by 

 conveying specific infectious diseases. This is peculiarly true 

 in the case of older children and adults, inasmuch as very young 

 infants fortunately seem to have a very high natural degree of 

 immunity against the most common infectious diseases — an 

 immunity very rapidly lost after the first year of life. 



Tuberculosis is the specific disease most commonly trans- 

 mitted by milk, but because this disease is derived from the 

 animal we have considered it a separate problem. The common 

 point about all the rest of these diseases is that they are not 

 due in any sense to the condition of the cow that produced the 

 milk, but are due entirely to human contact infection at the 

 time or after milking is done, that is, between the time when 

 the milk leaves the cow and the time when it is swallowed by 

 the consumer. 



These facts about the transmission of infectious diseases 

 through milk are a comparatively recent discovery. Statistics 

 on these points go back only comparatively few years, but 

 when the facts are brought together they make a most powerful 

 indictment, not against milk itself, but against careless metb.ods 

 of producing and handling milk. Milk, as a rule, becOxTies 

 infected with the germs of specific infectious diseases on the 

 farm or in the dairy premises, or in process of transportation, 

 and not readily after its final arrival in the household. These 

 serious possibilities of milk infection are due to milk's peculiar 

 qualities as a germ food, and, hence its power of multiplying 

 the original amount of infection many times during the period 

 that the milk is being transmitted from producer to consumer 

 unless kept cold, when such multiplication does not occur. 



The total number of infectious diseases that may be trans- 

 mitted by milk is quite large, but for practical purposes we may 

 consider four. They are typhoid, diphtheria, scarlet fever, and 

 so called epidemic sore throat. 



The chief characteristics of transmission of contagious dis- 

 ease through milk, are : 



First, epidemics produced by them are practically explosive 

 in character in the suddenness of their onset. 



