82 MICROBES AND TOXINS 



The decomposition is generally only partial and to procure 

 the quantity of oxygen and energy necessary the anaerobes 

 have to attack large quantities of the food-stuffs. Such 

 behaviour is typical of ferments and accordingly the anaerobes 

 usually produce powerful fermentation. " Fermentation is 

 life without air," was Pasteur's dictum. It is in particular 

 the study of alcoholic fermentation which supports this 

 statement. When a yeast grows in a shallow mass of fluid 

 with an extensive surface its cells multiply abundantly : there 

 is a great increase in yeast protoplasm but little or no alcohol. 

 When inoculated on the contrary at the bottom of the fluid 

 without access of air, the growth is feeble but produces 

 alcohol in quantity, varying in proportion to the completeness 

 of the anaerobic conditions. The differences in the form and 

 functions of mucor when aerated or deeply immersed have 

 already been mentioned. Several microscopic plants, muce- 

 dineae and yeasts, exhibit a whole series of transitional forms 

 between aerobic and anaerobic growths. Anaerobic life appears 

 to be an asphyxial condition against which the microbe 

 contends or adapts itself by changing its manner of nutrition. 

 Not only the mucedineae and the yeasts but all living cells, 

 animal and vegetable, act like ferments and produce alcohol 

 when forced to live cut off from the air in presence of sugar. 

 Such is the case in the experiment of Pasteur and J. B. Dumas 

 with the plums kept under a bell-jar : they use up the air and 

 fill the jar with carbonic acid ; their sugar diminishes and they 

 become charged with alcohol. A similar case is that of ripe 

 fruits left to themselves in an atmosphere of limited volume, 

 as, for example, with the apples and pears kept in a closed 

 vessel in the experiments of Lechartier and Bellamy. Another 

 is that of seeds starting to germinate cut off from oxygen; 

 they produce alcohol, using up their reserve material (Maze's 



seizing upon the oxygen of certain compounds, in which there is in 

 consequence a slow progressive decomposition. This group of living 

 organisms is composed of ferments precisely similar to those of the first 

 group, living like them, assimilating like them carbon, nitrogen, and 

 phosphates, and like them requiring oxygen, but differing from them in 

 their power of doing without free oxygen gas and carrying on their 

 respiration with the oxygen derived from unstable compounds." 



