582 PATHOGENIC MICROORGANISMS 



for each L+ dose in the bulk toxin, and with each addition of antitoxin 

 to the mixture in bulk, it shall be immediately thoroughly shaken for 

 twenty minutes. After each addition to the mixture, or after the 

 original mixing, the preparation should stand at least twenty-four hours 

 in order to allow combination to take place before tests on guinea pigs 

 are made. Six guinea pigs are then injected receiving, respectively, 

 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 c.c. If all six guinea pigs die in seventy- 

 two hours, add 0.1 the former antitoxin used, mix and retest. Continue 

 this until the 5 c.c. pig survives ninety-six hours and at this point the 

 mixture is probably ready for filtering. After filtering, the mixture is 

 preserved until at least one-half of the 5 c.c. guinea pigs on each bulk 

 bottle survive ten days, but show definite diphtheritic paralysis there- 

 after. The human dose is 1. c.c., and three doses a week apart are 

 usually given. 



Bacteria Similar to Bacillus Diphtherise. BACILLUS HOFFMANNI 

 (Pseudodiphtheria bacillus). Hoffmann- Wellenhoff, 42 in 1888, and, at 

 almost the same time, Loeffler, 43 described bacilli which they had culti- 

 vated from the throats of normal persons and in several instances from 

 those of diphtheritic persons, which were in many respects similar to 

 true B. diphtheria, but differed from this chiefly in being non-pathogenic 

 for guinea-pigs. These organisms were at first regarded by some 

 observers as merely attenuated diphtheria bacilli. More recent inves- 

 tigations, however, prove them to be unquestionably a separate species, 

 easily different iable by proper methods. They differ from B. diph- 

 therise in so many important features, moreover, that the term "pseu- 

 dodiphtheria bacillus " is hardly an appropriate one for them. 



Morphology. Bacillus Hoffmanni is shorter and thicker than Bacillus 

 diphtheria. It is usually straight and slightly clubbed at one end, 

 rarely at both. Stained with Loeffler's blue it occasionally shows 

 unstained transverse bands; unlike B. diphtheriae, however, these bands 

 hardly ever exceed one or two in number at most. In many cultures 

 the single transverse band gives the bacillus a diplococcoid appearance. 



Staining. Stained by Neisser's or Roux's method, no polar bodies 

 can be demonstrated. The bacillus forms no spores, is non-motile, 

 and possesses no flagella. 



Cultivation. On the usual culture media B. Hoffmanni grows more 

 luxuriantly than B. diphtheria, developing even in first isolations from 



* Hoffmann-Wellenhoff, Wien. med. Woch<, iii, 1888. 

 " Loeffler, Cent. f. Bakt., ii, 1887. 



