BACILLI ALLIED TO DIPHTHERIA BACILLUS 409 



that, after the cure of the disease, the bacilli may persist in the 

 mouth for weeks, though they often quickly disappear. Roux 

 and Yersin found, by making cultures at various stages after 

 the termination of the disease, that these bacilli in the mouth 

 gradually become attenuated. 



I j, Martin, moreover, has shown that some races of diphtheria 

 bacillus are so attenuated that 1 c.c. of a twenty-four hours' 

 growth in bouillon does not cause death in a guinea-pig, yet their 

 true nature is shown not only by their miscroscopical characters, 

 etc., but also by the fact that on more prolonged growth they 

 form small quantities of toxin, which is neutralisable by diphtheria 

 antitoxin. The persistence of these non-virulent bacilli in the 

 throats of those who have suffered from the disease, and their 

 occasional presence in quite healthy individuals, may manifestly 

 be of importance in relation to the continuance of the infection 

 and the reappearance of epidemics of the disease. 



BACILLI ALLIED TO THE DIPHTHERIA BACILLUS. 



Bacteriological examinations carried on within recent times 

 have shown that the diphtheria bacillus is merely a member of 

 a group of organisms with closely allied characters which are 

 of common occurrence and have a wide distribution. The terms 

 "pseudo-diphtheria bacilli " and "diphtheroid bacilli " have been 

 applied in a loose way to organisms which resemble the 

 diphtheria bacillus microscopically, especially as regards the 

 beaded appearance. Such bacilli have been obtained from the 

 mouth, nose, skin, genital organs, and even from the blood in 

 certain diseases. They are to be met with sometimes in condi- 

 tions of health, and they have been obtained from many diverse 

 morbid conditions from skin diseases, from coryza, from 

 leprosy, and even from general paralysis of the insane. As 

 has been found with other groups, the differentiation is a matter 

 of considerable difficulty. Some are practically identical with 

 the diphtheria bacillus both morphologically and culturally, and 

 a few even give the characteristic reaction with Neisser's stain ; 

 others, again, differ in essential particulars. The fermentative 

 action on sugars 1 has also been called into requisition as a 

 means of distinguishing them, but the results obtained cannot 

 be said to be of a definite character, and further work is 

 necessary. It may be stated, however, that most observers 

 have found the diphtheria bacillus of all the members of the 

 group to 'be the most active acid-producer, though here the 

 1 Vide a paper by Graham-Smith, Journal oj Hygiene, vi. 286. 



