456 SPIRILLUM CHOLERA ASIATICS. 



short time, and the chances of spread of the disease are 

 correspondingly smaller. Further, the nutrient media 

 are rendered unsuitable for the multiplication of the 

 comma bacilli by drying of the surface, as well as for the 

 development of other bacteria which might possibly in- 

 fluence the individual predisposition. Finally, insects, 

 which are of such assistance in transporting the infection, 

 are absent. This result however will only occur where 

 there is a very great deficiency in the saturation of the 

 air with moisture, for example in a desert ; moderate 

 differences in the degree of moisture of the air can only 

 with difficulty exert a noticeable action. Diminution of 

 the moisture of the air, such as occurs, for example, in 

 Calcutta during the so-called "dry season " of the year 

 (November to April), can coincide very well even with 

 an increase of cholera if the paths of transport and the 

 individual predisposition are at the same time favourably 

 influenced by other factors. On the other hand, it is 

 conceivable that in a desert climate, such as is present 

 in Multan and Lahore during the greater part of the 

 year, and where everything dries up, as it were, under 

 one's eyes, the conditions favourable for the spread of 

 the cholera may only be present at most during the 

 somewhat moister or so-called "rainy" season (July to 

 October) . 



Rain. Very excessive and constant rains will, as a whole, 



cause a diminution in the number of the sources of in- 

 fection and of the paths of distribution. Where, as in 

 certain parts of India, and also in many villages and 

 habitations of the poor in European cities, all sorts of 

 filth and all infective dejecta are collected in the courts 

 and in the immediate neighbourhood of the houses, and 

 where attempts are never made to cleanse these surround- 

 ings, heavy rainfalls, which are powerful cleansers of the 

 surface of the earth, must lead to diminution and re- 

 moval of the sources of infection. Where, on the other 

 hand, the rainfall is slight and of short duration it can 

 hardly exert any direct action, and will at all events 

 occupy a secondary position as compared with other 

 important factors. 



