52 Comparative Studies 



group of micro-organisms, at the head of which is the 

 virulent L<ofiler bacillus, which may occur with several 

 distinct variations, as shown in cultures derived from dif- 

 ferent cases of diphtheria. The most marked differences 

 with regard to the L,6ffler bacillus are, first, long, slender 

 bacilli which show a tendency to the formation of rather 

 large, club-shaped organisms on blood-serum ; and second, 

 rather short, thick, ovoid bacilli which show the club- 

 shaped forms only occasionally. 



At the other extreme of this large group of micro-organ- 

 isms is the xerosis bacillus. Between these two extremes, 

 the types of which are the L,6ffler bacillus on the one 

 hand and the xerosis bacillus on the other, we have 

 many variations in type, as shown by the modifications 

 of biological and morphological characters. The organisms 

 which I have been studying, belonging more distinctly 

 to the group of pseudo-diphtheria, or Hoffmann bacilli, are 

 cultures Nos. 13, 20, 26, 27, 29 and 31. All the other cul- 

 tures studied belong to the group of xerosis bacilli. 



I believe it would be preferable to designate as Hofmann 

 bacilli all those so-called pseudo- diphtheria bacilli which 

 grow as a thick, creamy-white layer on agar-agar and on 

 blood serum. It is evident that these organisms are not 

 a-virulent LofHer bacilli, and therefore have no direct con- 

 nection with the disease processes in cases of diphtheria. 

 If they are capable of producing any lesions whatever 

 these are of a mild character and largely local in their 

 manifestation. The conditions existing in my nose and 

 throat at the time of isolating several of the cultures stud- 

 ied were of the nature of a mild catarrhal inflammation. 



In this connection I wish to thank Dr. A. C. Abbott, 

 Director of the Laboratory, for' valuable suggestions and 

 advice given during the investigation. 



