CHOLERA. 151 



made almost unaccountable leaps and divergencies, it has 

 been found to follow a very definite line of advance in the 

 course of the various epidemics, and although there may 

 have occurred sporadic cases which could be traced to no 

 definite source of contagion or infection, which have proved 

 a stumbling-block to many conscientious workers and ob- 

 servers, it is generally acknowledged that the evidence 

 accumulated through the researches of Koch and his fol- 

 lowers, both in Germany and in Great Britain, and of 

 several enthusiastic workers in France, can leave little doubt 

 in the minds of most of those who study the subject care- 

 fully, that cholera is a parasitic disease, that it travels along 

 the ordinary lines of commerce by railways, caravans and 

 ships, from the regions in which it is endemic to those 

 centres of trade and religion which, by their imperfect sanitary 

 arrangements, by the want of cleanliness of their inhabitants, 

 by meteorological conditions, and on account of bad water 

 supply, are ready for its reception and propagation. In the 

 European epidemics, of which up to 1885 there had been 

 six exceedingly severe ones during the present century, the 

 disease has, in every case, followed the lines of trade. 



Before the three last epidemics (1865, 1873, 1884) cholera 

 usually came to Europe by what may be called the Con- 

 tinental routes the caravan routes through Persia, Asia 

 Minor, and Russia ; but in the three last it came by the 

 Mediterranean or maritime route, first by land through 

 Egypt, brought there by Mecca pilgrims, and thence to 

 the seaports of France, Italy, and Spain, whence it gradually 

 made its way northward and inland, spreading over the 

 whole of Europe. 



At the mouth of the Yang-Tsze, as instanced by Macleod, 

 of Shanghai, cholera breaks out regularly at certain seasons 

 of the year, but he adduces evidence of great value to show 

 that although it may be imported directly from India, 

 between which and Shanghai there is at least weekly com- 

 munication, just as there is between India and the Nile delta 

 region, it is probably, in the strictest sense, an endemic disease 

 of that region. 



It can be readily understood, after the fearful ravages which 

 it made in places in which it was not actually endemic, 

 and after it had decimated the population in certain parts 

 of India, in Egypt, in the low-lying portions of Persia, and 



