176 BACTERIA. 



may accumulate in the neighbourhood of animal and vegetable decaying 

 matters most readily and give the micro-organisms opportunities for growth ; " 

 and he further says, " that whenever the water has a swift current, or is in 

 a constant state of change, both on the surface and in the ground, these con- 

 ditions occur less easily, or sometimes not at all, for the continuous current 

 prevents a localized concentration of nourishment in the fluid sufficient for 

 the pathogenic bacteria. The connection between the sinking of the 

 ground water, and the increase of many infective diseases, we might explain 

 thus : that with the sinking of the ground water, the current which exists in 

 it becomes very much lessened. Besides, the mass of water lying superfici- 

 ally at disposal will be considerably diminished, and therefore such a 

 concentration as I have described as necessary for the growth of the 

 bacteria will be produced much sooner." 



These conditions are necessarily closely associated with 

 temperature, with the nature of the sub-soil, and the pre- 

 vailing winds and air currents, and the consequent affection 

 of the quantity of moisture in the atmosphere, and the pro- 

 duction of rain must also be taken into account, as even the 

 transmission of the cholera organism is affected or interfered 

 with by great dryness of the atmosphere. Where there is 

 great dryness of the atmosphere the small quantities of 

 cholera dejecta, which are likely to be left unnoticed, and 

 therefore left disinfected by the attendants of the patient are 

 so rapidly dried that they are speedily rendered inert, and 

 cannot convey the infection further ; whilst the materials on 

 which, in ordinary circumstances, they would thrive, are so 

 dried on the surface that although the organisms may find 

 their way on to them in a living condition, there is not 

 sufficient moisture left to allow of the development of the 

 probably somewhat weakened organism. 



As Fliigge points out, such conditions " only occur where there is a very 

 great deficiency in the saturation of the air with moisture for example, in a 

 desert . . . It is conceivable that in a desert climate such as is present in 

 Mooltan and Lahore during the greater part of the year, and where every- 

 thing 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 some- 

 what moister or so-called ' rainy ' season (July to October). " 



Extreme wet may, however, exert an influence in interfer- 

 ing with the saprophytic growth of the organism, especially 

 if the rains be heavy and continuous. The conditions men- 

 tioned by Koch, as inimical to the collection of organic 

 material on which the organism may grow, are brought into 

 play, infective dejecta are removed from the surface soil, 

 from the surface drains and from the sewers, rapid and con- 



