1897J MICROSCOPICAL JOURNAL 161 



those slig-htly virulent or non-virulent bacilli which re- 

 semble it are the same species of bacterium. Out of seven 

 cultures from the i)harynx, there were five which pro- 

 duced a local edema and g-eneral disturbance in the guinea- 

 pig- when injected subcutaneously. Guinea-pig's which 

 had been injected with a relatively larg-e dose of anti-diph- 

 theritic serum were not rendered immune to the effects of 

 these cultures but the same dose of virulent diphtheria 

 culture was without effect. 



He also experimented with three cultures of the bacillus, 

 resembling- the diphtheria bacillus, isolated from typical 

 cases of xerosis conjunctiva'. Subcutaneous injections, 

 in g-uinea-pig-s of medium size, of one to three cubic cen- 

 timeters of a 24-hours bouillon culture, produced edematous 

 swelling-s which disappeared after forty-eig"ht hours, with 

 loss of appetite, weakness, etc. Guinea-pig's which were 

 rendered in a hig-h deg-ree immune to the diphtheria bacil- 

 lus showed no increased resistance to the bacillus of 

 xerosis. 



The author concludes that the anti-diphtheritic serum is 

 useful in differentiating^ the diphtheria bacillus from the 

 slig-htly virulent xerosis bacillus. He thinks the results 

 with the anti-diptheritic serum leave no doubt that the 

 xerosis bacillus does not belong- to the true species of diph- 

 theria bacilli but should be classed with one or more dis- 

 tinct varieties of bacilli. 



He does not claim to settle the question as to whether 

 everv bacillus which loses its effects in the presence of 

 the protective property of the anti-diphtheritic serum is 

 the true diphtheria bacillus, but leaves it to further re- 

 search. 



Whether the diphtheria bacillus with slig-ht virulence is 

 a common inhabitant of the conjunctival sac, he thinks can 

 be easily determined if all or most of the-cultures possess 

 sufficient virulenceto allow of control investig-ations. He be- 

 lieves, however, that most of such are org-anisms which 

 belong- in the class of xerosis Ijacilli. He does not-deny 

 that the true diphtheria bacillus may be found in the con- 



