530 



BIOLOGY OF THE MICRO-ORGANISMS. 



Formation of 

 ferments by 

 bacteria. 



Necessity for 

 free oxygen. 



Pasteur's 

 division into 

 aerobes and 

 anaerobes. 



pathogenic forms, which can only grow on certain 

 hosts, and which refuse to live on any other living 

 or dead substratum (such as the spirilla of relaps- 

 ing fever, or the bacilli of leprosj^), or which, at any 

 rate, require blood serum, or mixtures containing soluble 

 albumen, peptone, and salts. The greatest contrast to 

 these bacteria is formed by those which have been 

 described by Bolton* (bacillus erythrosporus, micro- 

 coccus aquatilis, &c.), which find sufficient nutrient 

 material to enable them to grow in enormous numbers 

 even in pure distilled water. As in all their other vital 

 functions, so here, the bacteria present conditions which 

 render it impossible to treat them in a schematic manner. 

 The number of suitable nutrient materials is increased 

 in the case of many species of bacteria by the fact that 

 they produce ferments which can transform insoluble 

 substances into soluble and diffusible ones. Coagulated 

 albumen, solidified gelatine, starch, and di-saccharates 

 can be transformed by means of peptonising, diastatic, 

 and inverting ferments into soluble and assimilable 

 nutrient materials. As regards this production of 

 ferment also the various species of bacteria show great 

 differences both qualitatively and quantitatively. 



The bacteria also behave very differently with regard 

 to oxygen. Pasteur was the first to observe that there 

 were bacteria which did not require free oxygen for their 

 life and multiplication, but, on the contrary, could earn- 

 on their vital functions in the absence of oxygen, and, 

 indeed, the presence of that gas might interfere with 

 their multiplication and their vital phenomena. Pasteur 

 gave effect to this distinction by his division of the bac- 

 teria into " aerobes " and " anaerobes." The surprising 

 fact that life could occur without oxygen was also soon 

 confirmed by other observers, such as Nencki, Praz- 

 mowski, Rosenbach, &c., and though Gunning asserted 

 that in none of these experiments was the oxygen 

 sufficiently removed, and thus no complete anaerobiosis 

 existed, nevertheless these objections cannot hold ground 

 against the recent experiments by Nencki and Lachewicz ; 



Gott. hyg. Institut. Mitgetheilt in Zeitsckr.f. Hygiene, vol. i. 



