IO2 PRACTICAL DAIRY BACTERIOLOGY 



half-a-dozen, of these microscopic germs make their way into 

 the milk, they find the milk such a favorable condition for 

 growth that they multiply rapidly and, in the course of a few 

 hours, become indefinitely numerous. By the time this milk has 

 reached the consumer they may have become so abundant as to 

 constitute a very considerable source of danger. It is beyond 

 doubt this multiplication of bacteria in the milk that explains the 

 violence of the milk typhoid fever epidemics. Wherever the 

 germs are present at all they are likely to be abundant from 

 this growth, and under these circumstances a large proportion 

 of those drinking the milk are sure to be infected. In this re- 

 spect the conditions are very different from the distribution of 

 the typhoid by water. In water the multiplication of the germs 

 is slight, and they rarely become very abundant. As a rule, 

 water epidemics of typhoid, though wide-spread, affect only a 

 small portion of those drinking the water, while a much larger 

 proportion of those drinking milk are thus infected. It is, 

 therefore, of the utmost importance for the dairyman to re- 

 member that typhoid must be absolutely excluded, for the en- 

 trance of a very few germs is a source of danger; a condition 

 quite different from that of tuberculosis, where the presence of 

 a small number of germs in the milk is not a source of danger 

 to anyone. The milk has much less chance of becoming in- 

 fected with typhoid bacteria than with tuberculosis germs, but 

 when it does occur the danger to the consumer is very much 

 greater. 



Since typhoid fever epidemics due to milk are frequent, 

 health officials are sometimes called upon to trace their origin. 

 The steps in such a problem are simple. In tracing the source 

 of a typhoid epidemic the first step is to determine the limits 

 of the disease, and if possible to find whether the cases occur 

 in such a way as to exclude the water supply as a source of 

 contamination. If all of the cases occur rapidly, new cases 

 failing to appear after two or three weeks, a single temporary 



