43 



Diphtheria 



line rather than an acid reaction by their growth in bouillon. The 

 pseudo-diphtheria bacilli were found in about i per cent, of throats 

 examined in New York ; they seem to have no relationship to diph- 

 theria, and are never virulent. 



Morphology. -This micro-organism bears a more or less marked 

 resemblance to Bacillus diphtherias, but differs in certain particulars 

 that usually make it possible to recognize and identify it. It is 

 shorter and stouter than its relative, is straight, usually slightly 

 clubbed. It usually stains intensely, and commonly shows but one 

 unstained transverse band. When the bacilli are short and have a 

 single band, they may resemble cocci. When longer they may show 

 two transverse bands. 



There are no flagella and no spores. 



v- 





Fig. 161. Pseudo-diphtheria bacilli. 



Staining. -The organism stains intensely and more uniformly 

 than Bacillus diphtheriae. When colored by Neisser's or Roux's 

 method, no metachromatic end bodies can be denned. 



Cultivation. -The organism is usually discovered in smears made 

 for the diagnosis of diphtheria, and sometimes occasions considerable 

 confusion through its cultural similarities and morphologic resem- 

 blances to Bacillus diphtheriae. It grows more luxuriantly upon the 

 ordinary culture-media than B. diphtheriae. The colonies are larger, 

 less transparent and whiter, as seen upon agar-agar. In bouillon 

 there is more marked clouding and less marked pellicle formation. 

 Upon Loffler's blood-serum the cultures are too much alike to be 

 easily differentiated. 



G. F. Petri* found no substances in nitrates of cultures of Hof- 

 mann's bacillus capable of neutralizing diphtheria antitoxin; he also 

 found that horses immunized with large quantities of nitrates of the 

 * "Jour, of Hygiene," April, 1905, vol. v, No. 2, p. 134. 



