PLAGUE. 107 



usually somewhat straighter than those which occur 

 in the stools and the " fish in stream " arrangement is 

 not marked. They will not stain by Gram's method. 



c. The addition of a small quantity of pure strong 

 sulphuric acid will give a pink or crimson tint. This is 

 the " cholera-red " reaction and is caused by the action 

 of sulphuric acid on indol in the presence of a minute 

 quantity of a nitrite; many other organisms (e.g., the 

 bacillus coli) produce this colour after the addition of 

 a nitrite, very few without it. The cholera vibrio pro- 

 duces nitrites as well as indol. 



INTERPRETATION OF RESULTS. 



In a case in which the above phenomena are ob- 

 served, the inference that the patient is suffering from 

 true Asiatic cholera is so strong that the authorities 

 should be notified and the fullest precautions taken. 



A case in which they are absent is almost certainly 

 not one of true cholera. 



PLAGUE. 



The bacteriological diagnosis of plague should be 

 made by an expert ; not because it is difficult, but be- 

 cause so much hinges upon it, at least in this country. 

 A brief account of the method by which a practitioner 

 who was unable to obtain expert help might proceed 

 may not be out of place. 



The plague bacillus is a short and rather thick rod 

 which occurs in vast numbers in the bubo, in the blood, 



