PSEUDO-DIPHTHERIA BACILLUS. 371 



Loftier, in 1887, was the first to describe a bacillus having closely 

 the characters of the diphtheria bacillus, but differing from it in its 

 want of virulence. He looked upon it as a distinct species, and gave 

 it the name of the pseudo-diphtheria bacillus. Hofmann, in 1888, 

 published an account of his investigations on this subject. He 

 obtained the pseudo-diphtheria bacillus from the throat in healthy 

 conditions, and also in non-diphtheritic affections. His conclusions 

 with regard to the distinct character of this bacillus were similar to 

 those of Loffler. Since that time the organism has been the subject of 

 much research and discussion. Roux and Yersin, on the other side, 

 found a " pseudo-diphtheria " bacillus corresponding in all its characters 

 with a greatly attenuated diphtheria bacillus, and concluded that it was 

 really of the same nature. They failed to make it virulent by any 

 method ; but this result was also obtained in the case of artificially 

 attenuated diphtheria bacilli. Biggs has found that there are two 

 varieties of pseudo-diphtheria bacilli, both differing from the true 

 diphtheria bacillus ; one of these produces an acid reaction in broth 

 containing glucose, whilst the other does not. According to his 

 statistics the two varieties appear to occur with about the same 

 frequency, and these observations have been in the main confirmed by 

 Cobbett and Phillips. Hewlett and Knight find evidence that a true 

 diphtheria bacillus may be modified so as to show the microscopic and 

 cultural characters of the pseudo-diphtheria type, this evidence being 

 obtained both by successive examinations of the throat after diphtheria 

 and by modifying cultures artificially. 



As a rule the appearances of the colonies and the 

 microscopical 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 conclusive, but we con- 

 sider 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-viru- 

 lent, 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, 



