DISEASE GERMS IN MILK 



99 



epidemic gives every indication of being confined to a single 

 instance of infection. They differ notably from typhoid fever 

 epidemics due to the water supply in the fact that the latter 

 are much more lasting, continuing for weeks and months. No 

 milk epidemic has, as yet, been known to last long, and all 

 seem due to one brief period of infection. The explanation of 

 this is natural. The chance of infection of milk with typhoid 

 fever bacteria is always a remote one, and it is never likely to 

 continue for any considerable length of time. In other words, 



FIG. 38 TYPHOID BACILLI 



Ordinary culture 



plagella not shown 



(Lehmann & Neumann) 



FIG. 39 TYPHOID BACILLI 



Showing flagella 

 (Lehmann & Neumann) 



the infection is confined to one or two days only, after which 

 the milk from this same source usually becomes normal again. 

 A single day's infection will produce the short, sharp type of 

 epidemic above referred to. 



We must next ask for the source by which milk becomes in- 

 fected with typhoid fever germs. It must first be recognized 

 that only one source of typhoid fever germs is known, viz: the 

 intestinal contents of a typhoid fever patient. They pass out 

 of the body in the faeces or from the mouth and are distributed 

 by various means. The methods by which they get into the 

 milk are, of course, not always the same, and they may be 

 grouped under three heads: 



