DISSEMINATION. 473 



met attempts to limit the extension of cholera by 

 quarantine measures. Cholera extends from coun- 

 try to country along the lines of travel. In some 

 instances it has been possible to trace the origin 

 of widespread epidemics to the delta of the Ganges, 

 a region in which the disease is endemic. Pilgrims 

 from India carry the infection to Mecca, and pil- 

 grims from Egypt carry it to their native land on 

 their return from Mecca. Either from Egypt, or 

 through Arabia, Asia Minor and Southern Eussia 

 or Turkey, cholera has, with more or less rapidity, 

 extended to Western Europe. The development of 

 rapid transit has increased the rapidity with which 

 cholera may extend. From Europe the disease has 

 been carried to various ports of the western conti- 

 nent, Canada, the West Indies and southern ports 

 of the United States, from which extension has oc- 

 curred to different sections. Of six widespread 

 epidemics of the past one hundred years, three 

 have involved the United States, reaching consid- 

 erable proportions. The means of introduction is 

 not always apparent. 



As in typhoid, two types of epidemics are known, 

 the two often being associated: First, that caused 

 by water infection, and, second, that in which the 

 disease spreads by direct and indirect contact. The 

 explosive character of an epidemic caused by in- 

 fection of a water supply is much more striking 

 than in the case of typhoid fever. In large cities 

 hundreds, or thousands, may be striken within a 

 day. The brief incubation period, from twelve to 

 twenty-four hours, contributes to the acuteness of 

 the outbreak. The distribution of a "water- 

 borne" epidemic corresponds with the distribution 

 of the infected water. A remarkable occurrence il- 



