CHAPTER XXIII. 



Bacterium (Syn. Bacillus) Diphtheriae — Its Isolation and Cultivation — 

 Morphological and Cultural Peculiarities — Pathogenic Properties — 

 Variations in Virulence — Bacterium Pseudodiphtheriticum — Bacterium 

 Xerosis — Diphtheria Antitoxin. 



Feom the gray-white deposit on the fauces of a diph- 

 theritic patient prepare a series of cultures in the following 

 way: 



Have at hand five or six tubes of Loffler's blood-serum 

 mixture. (See chapter on Media.) Pass a stout platinum 

 needle, which has been sterilized, into the membrane and 

 twist it around once or twice, or brush it gently over the 

 surface of the membrane. Without touching it against 

 anything else rub it carefully over the surface of one of the 

 serum-tubes; without sterilizing it pass it over the surface 

 of the second, then the third, fourth, and fifth tubes. Place 

 these tubes in the incubator. Then prepare cover-slips 

 from scrapings from the membrane on the fauces. If the 

 case is one of true diphtheria, the tubes will be ready for 

 examination on the following day. 



The reason that plates are not made in the regular way 

 in this examination is that the bacillus of diphtheria develops 

 much more luxuriantly on the serum mixture, from which 

 plates cannot be made, than it does on the media from which 

 they can be made. The method employed, however, insures 

 a dilution in the number of organisms present, and this, in 

 addition to the fact that the blood-serum mixture is a much 

 more favorable medium for the rapid development of the 

 diphtheria organism than of the other organisms present, 

 (454) 



