SOURCES OF ENERGY IN ANAEROBIOSIS 173 



and Kirk, 1941) and in Euglena proxima (Glaser and 

 Coria, 1935). 



The sugar that is usually at the disposal of the above- 

 mentioned organisms under natural conditions is glucose, 

 and this sugar is also the one quite generally used under 

 experimental conditions. But, as the data assembled in 

 Table 21 demonstrate, a variety of other simple sugars 

 may also be utilized by many protozoa in fermentations 

 in the presence of air. Of the common hexoses, glucose, 

 mannose and fructose are the ones most commonly used, 

 and galactose the least. The disaccharides maltose and 

 saccharose are frequently fermented, lactose only rarely, 

 but the trisaccharide raffinose seems to be easily metab- 

 olized. Pentoses are the least used of sugars. (Some data 

 on glucose consumption are gathered in Table 22.) 



M e t a z a . Very little information is available con- 

 cerning the use of simple carbohydrates by metazoa in 

 anaerobic metabolism, either in the absence or the pres- 

 ence of air. Such substances are usually not stored in 

 large amounts in the body. Satisfactory feeding experi- 

 ments under conditions of severe lack of oxygen are in 

 most cases not possible, either because the animals then 

 do not take food readily, or because the presence of bac- 

 teria in the surroundings renders it impossible to gather 

 reliable data on the disappearance of sugar from the 

 medium. 



Kramer (1937) kept isolated tentacles of Anemonia 

 sulcata under anaerobic conditions in a medium contain- 

 ing 0.1 per cent glucose and ascertained that considerable 

 amounts of carbon dioxide and organic acids were form- 

 ed, but he did not study to what extent the sugar was 

 actually consumed. 



Mej^erhof and Schulz (1929) state that the anaerobic 

 acid production of isolated nerves of Maja squinado per- 

 sists longer in a sugar-containing than in a sugar-free 

 medium. 



