42 BACTERIOLOGY. 



like that of Cladothrix, the Actimomyces fun- 

 gus must after all be regarded as a mould. 

 Till recently the tubercle bacillus was re- 

 garded as an especially typical bacterium, and 

 when stained differentially, the shining red 

 band stood out in fine contrast with the blue 

 background, a most beautiful example of a 

 bacillus. But Roux, Nocard and Metschni- 

 koff, as well as more recently E. Klein and 

 Maffucci, observed that the tubercle bacilli ob- 

 tained from cases of fowl tuberculosis exhibit 

 a sort of branching ; and Metschnikoff , laying 

 emphasis upon the filament-forming character 

 of the organism, placed it with the Lepto- 

 thrichece or Cladothriche<z and called it Sclero- 

 thrix. For some time evidence has been 

 accumulating that the opinion of Koch, who 

 had regarded the organism as forming endo- 

 spores and had hence correctly conferred 

 upon it the name of tubercle bacillus, and his 

 corresponding schematic figure were errone- 

 ous. Upon the basis of further investigations 

 which revealed branching even in the microbe 

 of mammalian tuberculosis, investigations 

 supplemented by my pupil Fischel, I have 

 arrived at the definite opinion that the tubercle 

 bacillus is the parasitic growth-form of a pleo- 

 morphic mould and is not a true bacterium at 

 all, but, in respect to its morphology, is closely 



