THE MICROBES OF HUMAN DISEASES. 107 
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 feeces, 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 (Bucillus 
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-watvr 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, 
