38 ESSAYS ON BACTERIOLOGY. 



bacillus of Lceffler is the specific germ, and that there 

 is but one cause of genuine diphtheria. The recent 

 researches of Welch and Abbott in Baltimore have 

 confirmed this view. It is, however, possible that a 

 pseiido-membranous disease may be excited by other 

 agents than the diphtheria bacillus, and Prudden 

 wisely suggests that it is not best to close the discussion 

 until all the evidence is in. 



As to the germs of pneumonia: , The pneumococ- 

 cus, or pneiimo-bacillus, of Friedlander has about lost 

 its significance. Of it Frsenkel says: "E^either mi- 

 croscopic investigation, nor culture, nor transmission 

 having furnished sufiicient proofs for the assertion 

 that the pneumococci play a decided role in the origin 

 of pneumonia, we cannot recognize them as the causal 

 factors of this disease." He adds: "It may, there- 

 fore, be assumed that they are at any rate related to 

 the said affection, and it may not be amiss to regard 

 them (like the streptococci in typhoid) as subsequent 

 settlers on a soil prepared and properly fitted by the 

 activity of some other micro-organisms." 



The pneumoeoOcus of A. Frsenkel, on the other 

 hand, which, it will be remembered, was first discov- 

 ered by Sternberg, has risen immensely in importance. 

 Of it I cannot do better than quote again the words of 

 Carl Frsenkel. "It belongs," he says, "to the most 

 virulent of infectious micro-organisms known. It is 

 proved to exist in over 90 per cent, of all cases of 

 pneumonia. The fact of its being missed here and 



