XON-SPORING BACILLI 247 



Grows best at 37 C. ; growth at 22 C., but not at 

 20 C. 



Isolation. Take sterile swab, nib on throat, then rub over 

 serum in tube, and incubate for 18 to 24 hours at 37 C. 

 Take platinum loop and rake all over surface of serum, 

 and then make a film and stain with Loemer's methylene- 

 blue or Neisser. Distinguish from Hoffmann's bacillus, 

 which is shorter and plumper, does not produce acid in 

 glucose, is non-pathogenic to guinea-pigs, and does not show 

 granules with Neisser. (B. diphtherias at times does not 

 give Neisser, and occasionally pseudo-B. diphtherias does 

 stain with Neisser.) The only sure method of differentia- 

 tion is toxicity of culture ; guinea-pig killed in 24 to 48 to 

 72 hours by injection of toxin of true B. diphtherias. 



In the serum-water medium of Hiss, plus I per cent of 

 glucose, laevulose, galactose, maltose, lactose, saccharose, 

 mannite and dextrin, B. diphtheriae produces acid in all 

 except with mannite, lactose, and saccharose ; B. xerosis 

 produces acid with all except mannite, lactose, and dextrin ; 

 B. Hoffmanni does not produce acid with any. 



The saccharose and dextrin media therefore serve to 

 differentiate : B. diphtheria, acid with dextrin, not with 

 saccharose ; B. xerosis, acid with saccharose, not with 

 dextrin ; B. Hoffmanni, acid with neither. 



In Vincent's angina, B. fusiformis is found : an anaerobe, 

 Gram-negative, longish, and swollen in the middle. 



B. xerosis is found in the conjunctiva, and is practically 

 identical with the B. diphtherias : it is non-pathogenic to 

 animals ; produces no toxin ; does not form acid with 

 glucose, but ferments saccharose. 



Habitat. Mucous surfaces, mouth, throat, nose, con- 

 junctiva, larynx, middle ear, vagina. 



Thermal Death-Point. Forty-five minutes at 55 C., 

 (moist heat) ; dry membrane, i hour at 98 C. 



Resistance. Lives six to eight weeks on agar, five to six 

 months on serum, twelve to fifteen months on dextrose 

 serum. In dried membrane retains vitality for months. 



Pathogenicity. -Guinea-pigs die in from two to three 

 days after subcutaneous injection of young broth culture. 

 Nephritis and paralysis are observed, but the characteristic 

 feature is enlarged and haemorrhagic condition of the 



