1 84 BACTERIOLOGY. 



mucous membrane, in conjunctivitis fibrin osa, 

 and (by Abel) in wound diphtheria. Virulent 

 diphtheria bacteria have also been observed, 

 existing as ceco-parasites in healthy individ- 

 uals ; these may, under special conditions, in- 

 duce self-infection or be the means of conveying 

 the disease to susceptible persons, particularly 

 to children. 



Virulent diphtheria germs lose their viru- 

 lence under cultivation, especially in agar cul- 

 tures, while their growth becomes at the same 

 time more luxuriant, that is to say, more sap- 

 rophy tic. Similar but non-virulent bacteria are 

 sometimes found occurring spontaneously in 

 man, Loffler being the first to discover this fact. 

 Many bacteriologists, among them Roux, Yer- 

 sin, C. Frankel, and Hueppe,' regard these 

 so-called pseudo-diphtheria bacilli merely as 

 true diphtheria germs which have become im- 

 potent and saprophytic, while Loffler, Hof- 

 mann, von Wellenhof and Escherich regard 

 them as a totally distinct species. The pseudo- 

 diphtheria germs do not alter the reaction of 

 alkaline bouillon while the diphtheria bacteria 

 render it acid at the outset, but it afterwards 

 becomes again alkaline. 



Cholera asiatica. The so-called comma 

 bacilli found in this disease were discovered by 

 Koch in 1883 (Fig. 27). They occur in the form 



