346 GERM-THEORY OF DISEASE. 



interfere with the development of the moulds are favourable to them, 

 ; n I it is consequently with this group that we have alone to concern 

 ourselves in connection with the Germ-Theory of Disease. The 

 colourless Schizophytes or Schizomycetes, as they are also termed, 

 present many difficulties to the investigator on account of their 

 extremely small size. 1 



Various generic forms have been distinguished, such as Micro- 

 coccus, embracing the minutest globular or oval forms often in 

 chains ; Bacterium, short, rod-like forms ; Bacillus, longer rods ; 

 Leptothrix, long jointed threads; and in addition various spiral 

 forms, Spirillum, ■ Spirochate. The constancy of these forms has 

 been defended by some authorities ami denied by others, but the 

 recent researches of Zopf on Claclothrix and Beggiatoa indicate that 

 all of these so-called genera may be merely different stages of 

 development of higher members of the same group of Fungi. Thus 

 the thread-like Cladothrix and Beggiatoa, two of the commonest 

 aquatic fungi of cosmopolitan occurrence, give rise in the interior of 

 the threads to Micrococcus or Bacterium-like spores which may 

 grow out into Bacillus- and Leptothrix-like forms, or may first 

 multiply themselves rapidly in a motionless or zoogloea condition. 

 Again in both the adult threads may undergo a retrogressive 

 development, becoming divided up into shorter or longer pieces 

 (Bacillus- or Leptothrix-like), which again may fall into still shorter 

 rods. Spiral forms are also described as belonging to the genetic 

 cycle of Cladothrix and Beggiatoa. These are formed by the break- 

 ing up of a thread which had become spiral in virtue of one-sided 

 growth, and the resulting fragments are Spirillum-like or Spirochate- 

 like, according to the closeness of the spiral and thickness of the 

 portion of the thread to which the fragment belonged. Whatever 

 their length and shape the fragments foi'med in the course of this 

 retrogressive development attain cilia on becoming free. It is simi- 

 larly asserted that all of the Micrococcus, Bacterium, and Bacillus- 

 like forms found in the mouth belong to the genetic cycle of 

 Leptothrix buccalis. 



A similar inconstancy of physiological peculiarities has also been 

 asserted by recent observers, so that the view that disease-producing 



l They are usually measured for convenience sake by micro-millimetres, one of these units 

 being the j-j 1 ^ mm. = ^-j-J-j-^ inch, and represented by the sign ix.. 



