346 GERM-THEORY OF DISEASE. 
interfere with the development of the moulds are favourable to them, 
en lit 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." 
Various generic forms have been distinguished, such as Miero- 
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 and denied by others, but the 
recent researches of Zopf on Cladothrix 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. Thugs 
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, accurding 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 formed in the course of this 
retrogressive development attain cilia on becoming free. It is simi- 
larly asserted that all of the Aficrococcus, 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 
1They are usually measured for convenience sake by mnicro-millimetres, one of these units 
being the 531455 mm. = 547 inch, and represented by the sign p. 
