452 AGEICULTUEAL AND INDUSTEIAL BACTERIOLOGY 



when delivered. It is evident also that the number of bac- 

 teria present will be a function of the time which has 

 elapsed since the milk was drawn. It will also be affected 

 by the care with which it has been handled and whether 

 or not it has been pasteurized. 



It should be recalled that milk is an excellent medium for 

 the growth of many microorganisms, and if given the oppor- 

 tunity they will multiply until great numbers are present. 



Disease Bacteria in Iililk. — ^From the standpoint of the 

 sanitarian, the fact that there are certain kinds of bacteria 

 present in the milk may be more important than the num- 

 bers. Large numbers of lactic acid bacteria, for example, 

 may be without particular significance from the standpoint 

 of health, but the presence of any disease-producing organ- 

 isms is apt to cause human infection. Evidently the most 

 important of the diseases transmitted by milk are various 

 diarrheas and dysenteries of young children. Whenever 

 there has been a marked improvement in the character of 

 the milk supply of our larger cities, there has been coinci- 

 dently a marked decrease in the death rate, particularly in 

 the morbidity rate among young children. Apparently the 

 alimentary tract of the child is more susceptible to an 

 infection of this kind than that of the adult. Particularly 

 in summer when bacteria are apt to multiply to large num- 

 bers in milk there is trouble with so-called "summer com- 

 plaint. ' ' The only safe procedure when milk does not come 

 from a source which is entirely above suspicion is to pas- 

 teurize it. 



Among the diseases attacking adults and transmitted by 

 milk is typhoid fever. A number of epidemics of this dis- 

 ease has been traced to infected milk. It is usually not diffi- 

 cult to differentiate epidemics spread by milk from those 

 which have their origin in contaminated water by a study 

 of the distribution of the cases and by the fact that in most 

 such epidemics a considerable proportion of the victims are 



