208 MICRO-ORGANISMS AND FERMENTATION. 



Their fermentative power is not connected with the formation 

 of budding gemmae, for these have not been observed in 

 either Mucor Mucedo or M . stolonifer. This form of fermenta- 

 tion has been regarded as a special kind of breathing. Unlike 

 normal respiration, such as is performed by every organised 

 being the absorption of oxygen and exhalation of carbon 

 dioxide it can take place in the absence of free oxygen. The 

 oxygen in the cell contents makes fresh intra-molecular linkings, 

 with the result that the carbohydrates, and more particularly 

 the sugars, become disintegrated, so that not only carbonic 

 acid but also alcohol is produced. Adopting the term suggested 

 by Pfliiger, the process is known as intramolecular respiration. 

 This conception implies that the fermentative change pro- 

 duced by Mucor, which is only possible in the absence of free 

 oxygen, differs essentially from that brought about by yeast, 

 which can go on either in the presence or absence of free oxygen, 

 Wehmer's experiments with two species of Mucor (M. race- 

 mosus and M. japonicus) have shown, however, that the pro- 

 duction of alcohol was not diminished by the constant bubbling 

 of air through the liquid, nor yet when the fermentation is 

 carried out in very thin films of liquid with a large exposed 

 surface. In other directions the two kinds of fermentation 

 possess characteristics in common, and the collective evidence 

 makes it difficult to regard the processes as essentially different. 

 On the other hand, Palladin and Kostytschew and others have 

 proved that the two fermentations are not identical. A 

 special alcohol enzyme, such as that isolated from yeast, ha& 

 not been isolated from Mucor mycelium. Kostytschew ob- 

 served, however, that the mycelium of M . racemosus, which 

 had been killed by treatment with acetone, was able to produce 

 an amount of carbon dioxide equal to that evolved by the 

 living cells. M . racemosus, Hansen's M . negl&ctus and (accord- 

 ing to Saito) Rhizopus japonicus, var. angulosporus, and RJi. 

 Tamari are the only species capable of inverting and fermenting 

 a cane-sugar solution. This was proved by Fitz for M . race- 

 mosus, and confirmed by Hansen and others. The great 

 majority of species are, however, able to ferment maltose, 

 invert sugar, and dextrose. 



Considerable diversity may be observed amongst the 



