294 Cholera in Relation to Certain Physical Phenomena. [part i. 



minimum degree of prevalence at the period of minimum temperature, and a sudden 

 diminution from the maximum prevalence of cholera takes place contemporaneously 

 with the setting in of the colder weather. On the other hand, close association of 

 individuals must also be favoured by the crowding incident on the conditions of the 

 rainy months of the year when cholera is most apt to occur. As, however, the heavier 

 and more continuous rainfall of Lower Bengal, with the correspondent increased crowding 

 together of the people, is contemporaneous with a marked diminution of the disease, 

 the general weight of evidence remains opposed to the doctrine of direct contagion. 



(2) Assuming the water-level registers to give a fair general indication of the fluctuation 

 of the water used for domestic purposes in the different stations where observations were 

 conducted, the theory of the spread of the disease through the medium of drinking-water 

 gains greater support in the non-endemic area than in Lower Bengal. A glimpse at 

 the diagrams representing the variation in the water-level of different localities in this 

 area will show that the disease undoubtedly attains its maximum shortly after the 

 level of the water in the wells begins to rise ; hence, it might be inferred, when 

 sufficient time has elapsed for the choleraic material dispersed over the soil to find 

 its way by percolation into the wells, and when the water, being low, favours the 

 swallowing of the materies niorhi in a concentrated form. To this, however, it must 

 be added that a considerable proportion of the cholera of a station occurs before the 

 water-level in the wells is affected, especially in some stations where the wells 

 are very deep, and where the total annual fluctuation does not exceed a few inches. 

 In such cases it must be assumed, either that the cause of cholera was present in 

 the water before the percolated impurities could reach the well, or that the earlier 

 cholera of the season was derived from some other source than that furnishing the later 

 cases. With regard to the production of the " spring " cholera, again, it can hardly 

 be attributed to the percolation of choleraic impurities into the wells ; for the ground 

 appears to absorb all the rain that falls at this time, and in scarcely any of the 

 selected stations in the non-endemic area is it observable that the level of the well- 

 water is materially affected by this season's rainfall. 



It may, of course, be maintained that while all cases of cholera are not to be 

 referred to the effects of the ^percolation of choleraic impurities into sources of drinking 

 water, those phenomena which cannot be accounted for in this way are ascribable to 

 the effects of the direct introduction of the materials into the water, or other ingesta. 

 But before this can be accepted as a satisfactory explanation of the phenomena, it must 

 be shown that the facilities of introduction at different seasons and in different years 

 vary proportionately to the coincident prevalence of cholera. Until this has been done, 

 the theory seems to assume, that every year in which cholera is generally epidemic, 

 is at the same time a year in which there is an epidemic tendency to the direct 

 introduction of choleraic materials into sources of water supply. 



The streams and rivers must, however, receive a considerable amount of surface 

 impurities by every fall of rain ; and if it were true, as some advocates of the " water- 



