372 DIPHTHERIA. 



By the long-continued action of diffuse daylight in a dry room, he was enabled 

 to transform three species of virulent B. diphtheriae into forms which were 

 non-virulent and which could not be distinguished from the real Hofmann 

 bacillus. And again, by the aid of collodion sac cultures passed through one 

 •or two generations in the peritoneal cavities of rabbits ; by repeatedly trans- 

 ferring cultures of B. pseudo-diphthericus every second or third day to 

 nutrient broth and incubating at 37° C. ; and by cultivating the bacilli in broth 

 with staphylococcus pyogenes aureus, he was able to transform these apparent 

 Hofmann bacilli into bacilli having the characters of B. diphtheria, proving 

 virulent to guinea-pigs, and having their virulence counteracted by antitoxin. 

 Some pseudo-diphtheria bacilli, however, resisted all attempts at alteration, 

 and Lesieur therefore concludes that the majority of non-virulent diphtheria- 

 like bacilli met with are probably true B. diphtherias, which, through unknown 

 conditions, have lost virulence and undergone morphological alterations ; the 

 minority, only, can lay claim to the term " pseudo-diphtheria " bacilli, and 

 probably include several species. 



As a rule the appearances of the colonies and the micro- 

 scopical characters enable a rapid diagnosis to be made in 

 suspected diphtheria cases. In some cases, however, difficulty- 

 may be met with ; and in the first place, all the minor cultural 

 characters must be carefully examined, including the reaction 

 produced in broth. By this procedure it may be determined 

 whether the organism in question differs in any points from the 

 diphtheria bacillus. A positive result on inoculating a guinea- 

 pig (say with i c.c. of a 24 hours' broth culture) will be con- 

 clusive, but we consider that for all practical purposes an 

 organism having all the microscopical and cultural characters of 

 the diphtheria bacillus may be accepted as such. Even if it is 

 non-virulent, it is probably only an attenuated diphtheria bacillus. 

 L. Martin, moreover, has recently pointed out that some races 

 of diphtheria bacillus are so attenuated that i c.c. of a 24 hours' 

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

 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. Neisser also, as the result of an extended inquiry, 

 comes to a similar conclusion with regard to the virulence, and 

 considers that the characteristic staining, the morphological 

 characters, and the production of acid in glucose broth, when 

 taken together, afford conclusive evidence as to the identity of 

 the diphtheria bacillus. 



The question, however, has a special interest in regard to the 



