BACTERIA. 



77 



anaerobic species, whilst others multiply and induce butyric 

 acid fermentation when they have access to oxygen, aerobic 

 species. 1 



One of the first species to be minutely described is 



FIG. 21. Clostridium butyricum Prazm. (after PRAZMOWSKI) : J, vegetative state ; 

 c, short rods ; d, long rods ; at a and b, rods and filaments curved like vibriones ; B, 

 formation of " resting-spores " (Dauersporen) ; b, d, rods, previous to, c, e, during,/, g, 

 h, after the formation of resting-spores ; c, of an elliptical; d and h, of a lemon-like ; 

 e, g, of a spindle-like ; /, of a tadpole-like shape ; at a, rods still in their vegetative 

 state ; C, germination of resting-spores : the spore a expands into b ; c shows the 

 differentiation of the membrane into exo- and endosporium. The contents sur- 

 rounded by the endosporium issue from the polar fissure of the spore in the form of a 

 short rod (rf), which appears prolonged at e. 



PRAZMOWSKI'S Clostridium butyricum (Bacillus butyricus, Fig. 

 21). It occurs in the form of short and long rods, which may 



1 The pure cultivation of anaerobic bacteria may be carried out, for example, 

 in nutritive gelatines or agar, in well-filled test-tubes, these bacteria develop- 

 ing in the bottom layer. A better procedure consists in removing the air 



