CONTROL OF THE PUBLIC MILK SUPPLY 451 



the milk supply. In the smaller cities the health officer and members of 

 the milk inspection service do it all. 



The work is naturally divided into two parts: that which is done in 

 the country districts, usually within the sphere of authority of some other 

 official, perhaps a county health officer; and that which is carried on in 

 the city where the municipal health officer has sole jurisdiction. The 

 first step is to see that all cases of infectious disease of men and animals 

 are promptly reported. As regards the latter, veterinarians usually 

 willingly give helpful service, and cooperation in handling the cases is 

 generally mutually advantageous. The reporting of cases of human 

 contagion on the dairy farms and among the patrons and employees of 

 the creameries, country and city milk plants, etc., should be incumbent on 

 the dairymen and contractors who sell their milk or own the factories. 

 Besides, arrangements should be made with the local physicians and 

 health officer to report all cases of infection in the dairy district and with 

 the registrar, to report all deaths from contagion. It is for the municipal 

 health officer to see that all cases of communicable disease in the city are 

 promptly reported and that in each report the name of the milk dealer 

 is given. 



For collecting and recording this and other data relating to communi- 

 cable diseases suitable blanks and a system of office records should be 

 devised. All cases of contagion should be spotted on a large map of the 

 city. This gives a general view of the amount of infection and shows 

 the relative prevalence of the several diseases. Oftentimes, too, the 

 groupings of the cases on the map are suggestive of epidemiological re- 

 lationships. Thus, if the spots are scattered in all parts of the city where 

 the public water supply is used, the suspicion is aroused that the water is 

 infected and this seems more certain if no spots appear in a section of the 

 city not served by the public supply. A row of spots along a line of sewer 

 pipe may indicate that it is leaky and is polluting the wells in the street 

 in which it is laid. Sometimes the spots may be disposed about a well 

 in such a way that near it, they may be close together but further away 

 spread apart and at a greater distance disappear. A circle of short radius 

 and with the well as a center will circumscribe all the cases which denotes 

 that the neighborhood is using the water of an infected well. If the spots 

 mark out the delivery route of a milk dealer, the probability is that his 

 milk is infected. In the case of an infected route that is generally patron- 

 ized the spots may be so broadly scattered that doubt is cast on the 

 purity of the public water supply but careful inquiry will dispel it. Other 

 groupings have their proper interpretations. Also, the city should be 

 divided into several fairly large districts which should be kept intact 

 from year to year and the occurrence of cases of contagion in them should 

 be noted for careful study. Thus, the cases of contagion should be re- 

 corded as they occur week by week throughout the year over a series 



