168 AIR AND LIFE. 



to be had — oxygen in combination with one or the other of the sub- 

 stances dissolved in the liquid under consideration. This the micro- 

 organism uses for its wants. It withdraws this oxygen and releases it 

 from its fetters — not for the benefit of oxygen certainly, but for its own 

 advantage. As this release can not be effected without releasing also 

 at least one and often many other constituents which were combined 

 with the oxygen, they also are freed, and their escape is one of tlie 

 characteristic phenomena of fermentation. Let us take an instance, 

 that of alcoholic fermentation. This requires water in which cane or 

 grape sugar is dissolved (cane juice or grape juice). The microbe 

 removes from the sugar a portion of its component oxygen, thus decom- 

 posing it into free carbonic acid and alcohol. This is one instance 

 among a hundred. In all the process is fundamentally the same. In 

 all processes of fermentation a microbe is present which, unable to 

 otherwise obtain its requisite supply of oxygen, takes it by decompos- 

 ing the surrounding substances, changing them into new compounds, 

 containing in part the same elements as the original but differently 

 united. So we see that, upon the whole, anaerobic microorganisms, 

 which seem more or less to shun free oxygen and air, do really breathe 

 oxygen, as other organisms are wont to do. Thus, so far as some 

 organisms are concerned, life is not impossible where free oxygen is 

 wanting; and, on the other hand, wherever life is present, some method 

 exists by which oxygen may be secured. While anaerobic micro-organ- 

 isms seem to be exceptions, they fall under the general law that living 

 organisms must have oxygen. 



Between such anaerobic organisms and those which need free oxy- 

 gen many transition forms exist. It will be sufficient to recall the fact 

 that vegetable cells are aerobic and anaerobic simultaneously, since 

 they can produce alcoholic fermentation. "Let us place a beet root 

 in carbonic acid," says Duclaux, "we shall see it produce alcohol. 

 Cherries, plums, apples, all fruits containing sugar, entire saccharif- 

 erous plants, under the same circumstances do the same. Their sugar 

 is in part broken up into alcohol and carbon dioxide. The only differ- 

 ence between these cells and those of yeast is that the former are less 

 suited for anaerobic life, and the fermentation which they effect is 

 less complete than that effected by yeast, and they stop or die before 

 all the sugar has been transformed. But such differences are only 

 differences in degree.' 7 If we now turn to animal cells, we find that 

 they are also, in fact, anaerobic. Have we not seen that free oxygen 

 dissolved in the serum of the blood is toxic, and that it kills? That 

 the tissues do not breathe pure or free oxygen, but require to have it 

 offered to them combined with hemoglobin? And what is this, if not 

 true anaerobiosis? x Hence we must draw the inference that while all 



"The notion that animal cells are anaerobic was propounded by Pasteur. A. 

 Gautier, in 1893, took it up with some valuable arguments and experiments. These 

 experiments have shown that quite a number of well-known disassimilation products 



