24 MICRO-ORGANISMS AS PARASITES. 



native home. Notwithstanding the most patient researches, Koch 

 could not find the cholera bacillus in tanks which had been 

 polluted through the horrible disregard of all sanitary rules, shown 

 by the native Hindoos. On the bank of one such tank during an 

 outbreak of cholera, Koch found from 30 to 40 huts, containing 

 between 200 and 300 persons. The natives bathed daily in the 

 tank, drank of the water, and washed their clothes in it, and it 

 was the only receptacle for all drainage. The epidemic had 

 already reached its height when comma bacilli were found in the 

 tank, and their appearance in this case followed the epidemic. 

 Where, then, are we to look for the original source of these out- 

 breaks of disease? Koch says, "All authors are agreed that the 

 delta of the Ganges is the true home of cholera, and I have come 

 to the conclusion that this is the case. For the only district of 

 India where cholera prevails year after year is the delta of the 

 Ganges. In all other parts of India it shows marked variations, 

 and may even disappear altogether for a longer or shorter time." 

 On the map of the province of Bengal you can see this delta of 

 the Ganges, bordered on the west by the Hoghli river, and on the 

 east by the Brahmaputra. Over the whole of this district cholera 

 continually prevails. On closer examination of the map it must 

 strike one that the upper part of the delta is thickly covered with 

 towns, while the base of the triangle remains uninhabited. This 

 uninhabited stretch of land, called the Sunderbuns, embraces an 

 area of 7,500 square miles. Here the great rivers Ganges and 

 Brahmaputra break up hito a network of water-courses, in which 

 the sea-water, mingled with river-water, Hows hither and thither 

 with the tide, and at flood-time places large tracts of the 

 Sunderbuns under water. A luxurious vegetation, and an abundant 

 animal life, have developed in this uninhabited region, which 

 is inaccessible to man, not only on account of the floods and the 

 numerous tigers, but on account of the pernicious fever, which 

 attacks those who venture into this region even for a short time. 

 Here the cholera bacillus would find the most favourable 

 conditions possible for im])lanting itself, where all the drainage 

 from a thickly-populated country is washed down by the current 

 and mingles with the brackish water of the Sunderbuns, already 

 teeming with decaying matter. Jessore, from which the epidemic 



