444 SPIRILLUM CHOLERA ASIATICS. 



of infection are more especially limited by the fact that 

 the comma bacilli so readily die, either as the result of 

 Duration of drying or of overgrowth by saprophytes. As a conse- 

 quence it is, as a rule, only fresh dejecta, and objects 

 which have been recently soiled, that are dangerous ; all 

 materials which are completely dry, such as dry linen, 

 rags, letters, various kinds of wares, &c., maybe excluded 

 at once as possible carriers of infection. Where the 

 materials are moist, and in the case of fluids, the dura- 

 tion of the vitality of the comma bacilli which have reached 

 them depends upon their number, upon the number and 

 kind of saprophytic bacteria present at the same time, and 

 on various other external conditions ; but in any case it is 

 only rarely that it lasts for more than a few days. But it 

 is always possible that some materials, if kept moist and 

 in which the comma bacilli are preserved in a state of 

 almost pure cultivation, may act for some weeks as sources 

 of infection; for example, this is conceivable in the case of 

 moist cholera linen which is tightly packed, of moist 

 earth, &c., more especially when the temperature is low. 

 Points of From the mode of distribution of the comma bacilli in 



the r body int tlie body, and from the experiments as to their fate 

 when they are injected into the veins or subcutaneously, 

 we must draw the inference that natural infection occurs 

 as a rule only by the mouth. 



Modes of I R infection, therefore, we have to deal with two fac- 



transport. tors: on the one hand the sources of infection, which, 

 as we have seen, vary greatly in number and are limited 

 as regards resisting power; and on the other hand this 

 one point of entrance. All the conceivable w r ays are 

 evidently, however, not equally suitable for infection ; on 

 the contrary one or other mode of communication may 

 be completely excluded, while other modes vary as 

 regards their power under the influence of external con- 

 ditions. Currents of air are entirely unsuitable for the 

 transport of the infective agents, as by them only dry 

 particles are detached and carried away, while the comma 

 bacilli do not retain their vitality in the dry condition. 

 We may ex- The only exceptions in this respect are bubbles of water, 

 of^iVamd 81 ^ 8 which may be carried through the air. Hence a mode 



respiration. 



