THE MICKOBES OF HUMAN DISEASES. 197 



of this disease clearly indicates the presence of a 

 microbe, of which the chosen seat is the intestines, 

 whence it passes with the patient's faeces, and con- 

 stitutes the contagious element in places affected by 

 the epidemic. 



The first precise micrographic researches made on 

 this subject were those of the French and German 

 commissions sent to Alexandria in 1883. Koch, 

 member of the German sanitary commission, was 

 the first to describe the microbe which it has been 

 decided to consider as the producing agent of cholera. 

 He gave it the name of comma bacillus (Bacillus 

 komma), on account of its form. 



In order to see these bacilli in any number, a case 

 of malignant cholera must be observed. For this 

 reason, an unsuccessful search for this parasite has 

 often been made, since it cannot be distinguished from 

 the numerous other parasites found with it in the 

 intestines of cholera patients on the second or third 

 day. A small fragment of the rice-water evacuation 

 of cholera should be placed on a glass slide and 

 stained with methyl violet or methylene blue; the 

 superfluous liquid must be drained off, and the pre- 

 paration may then be examined under a magnifying 

 power of from 1200 to 1500 diameters, making use 

 of an immersion lens, on which light is thrown by an 

 achromatic condenser. 



The comma bacilli then present the appearance 

 shown in Fig. 87, and, in spite of the colouring matter, 



