.PATHOGENIC BACTERIA. 



time, occasionally several weeks after the patient has 

 apparently recovered; also that diphtheria bacilli are 

 occasionally found in the throat when there is an in- 

 flammatory condition without any pseudo-membrane, 

 and that they sometimes appear in an apparently healthy 

 throat, especially in children who have been associated with 

 cases of diphtheria. It has been found that bacilli some- 

 times occur in the throat which have all the morphological 

 and cultural properties of the diphtheria bacillus, but which 

 are devoid of virulence when tested upon animals, i. e. t 

 do not produce diphtheria toxin. Such diphtheria bacilli 

 have frequently been called pseudo-diphtheria bacilli. A 

 bacillus closely resembling the diphtheria bacillus, but with- 

 out virulence, has been found in xerosis of the conjunctiva. 

 It is called the xcrosis bacillus. If not a transformed diph- 

 theria bacillus, it is at least closely related. The diphtheria 

 bacillus is subject to wide variations in morphology, so that, 

 in dealing with unknown cultures where the forms of the 

 bacilli are not characteristic and injection into animals is 

 without result, it may be difficult to decide whether or not 

 the organisms are diphtheria bacilli. Consequently another 

 view with regard to pseudo-diphtheria bacilli has arisen. 

 While recognizing that avirulent diphtheria bacilli occur, 

 it is also claimed that a distinct pseudo-diphtheria bacillus 

 exists, different from the diphtheria bacillus, though re- 

 sembling it. It is shorter, stains more evenly, shows no 

 polar granules by Neissers method of staining, does not 

 produce acid in dextrose-bouillon, and is not pathogenic to 

 animals. It is found occasionally in the nose and throat, 

 and has no connection with diphtheria, according to this 

 view. 1 



1 The different sides of this question will be found fully discussed 

 by the following: Wesbrook, Wilson and McDaniel, Trans. Association. 

 American Physicians, 1900; Gorham, Journal Medical Research, Vol. 

 VI., 1900; A. Williams, Ibid., Vol. VIII., 1902; Denny, Ibid., Vol. IX., 

 1903. 



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