BACILLI ALLIED TO DIPHTHERIA BACILLUS 365 



at various stages after the termination of the disease, that these 

 bacilli in the mouth gradually become attenuated. 



L. Martin, moreover, has shown that some races of diphtheria 

 bacillus are so attenuated that 1 c.c. of a 24 hours' growth 

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

 nature is shown not only by their microscopical characters, etc., 

 but also by the fact that on more prolonged growth they form 

 small quantities of toxin, which is neutralised 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 ap- 

 pearance. 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 conditions 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 * has also been called into requisition as a means of distin- 

 guishing 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 difference seems to be one of 

 degree rather than of kind. The absence of the power of 

 fermenting certain sugars, notably glucose, may, however, be 

 accepted in any particular case as sufficient to exclude the 

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



