152 THE BACTERIA IN ASIATIC CHOLERA. [CH. 



be quite impossible to understand how it happens that the 

 attendants, nurses, and physicians of cholera-patients, those 

 that handle the cholera-dejecta, and the friends and relatives 

 living in the same room with the sick, remain so often 

 exempt. As von Pettenkofer has pointed out, the fact that 

 when in any locality cholera has assumed the epidemic 

 character and the attendants do become liable to cholera 

 does not prove that they contract it from the cholera-patient ; 

 for another explanation, namely, that the cholera-virus has 

 by that time become universally distributed in the locality, 

 is a good explanation. If the fresh cholera-dejecta 

 contained the materies morbi, or if, for instance, the 

 comma-bacilli were the cholera-microbes, then one case of 

 cholera should be sufficient to infect all those coming near 

 it. The experiments of Koch prove that the comma-bacilli 

 become inert and dead by perfect drying, e.g. when dried in 

 a thin layer on a coverglass or on silk threads ; but the 

 particles of cholera-dejecta thrown on the floor, on the 

 bed-clothes, &c., do not become so dry that the comma- 

 bacilli are dead. Indeed this is far from being the case. 

 Every one who is working in a laboratory knows that 

 accidental contamination with micrococci floating about in 

 the air is a constant source of annoyance ; expose a layer 

 of sterile nutritive gelatine in a glass dish for a few minutes 

 to free air-contamination, particularly during the summer 

 months, then cover it up ; or mix the gelatine first with a 

 little dust taken up from any part of the floor of the room 

 and make with it a plate cultivation and you will find in a 

 few days colonies of microbes bacilli, and particularly 

 micrococci. Yet micrococci are killed by perfect drying. 

 This proves that those contaminating micrococcus germs in 

 the air and dust were not dry. And the same holds good 

 of the comma-bacilli contained in the particles of the 



