SOURCES OF ENERGY IX AXAEROBIOSIS 179 



caecum of horses. These parasites have been known for 

 a long time to store very large amounts of glycogen 

 (Certes, 1889; Schulze, 1924, 1927; Trier, 1926; Usuolli, 

 1930; Weineck, 1931; MacLennan, 1934; Westphal, 1934; 

 Hungate, 1943). Both Westphal and Hungate found 

 that this reserve disappears very rapidly in starvation 

 experiments under anaerobic conditions. A comparison 

 between aerobic and anaerobic metabolism is not possible 

 in this case, since the animals are injured rapidly by 

 oxygen. 



Our knowledge concerning the importance of glycogen 

 as an energy reserve in parasitic rJiizopods is rather 

 scanty. A large glycogen vacuole is regularly found in 

 the cysts of lodamoeha. Dobell (1919) was the first to 

 point out that this represented a food reserve since the 

 polysaccharide disappeared slow^ly from cysts kept out- 

 side the host. Von Brand (1932) observed that the rate 

 at w^hicli this vacuole decreased in size and finally disap- 

 peared was identical under aerobic and anaerobic condi- 

 tions. He concluded that the polysaccharide was prob- 

 ably fermented in both cases. 



Concerning the glycogen content of human intestinal 

 amoebae the following points have been reported: Kue- 

 nen and Swellengrebel (1913, 1917) showed that the veg- 

 etative stages of these animals store some glycogen. Ac- 

 cording to the present writer's unpublished observations, 

 glycogen occurs in larger amounts and more regularly 

 in vegetative stages of Endamocha coU than in any other 

 amoeba of the same habitat. It is also known that culture 

 forms of Endamoeha histolytica have a much higher gly- 

 cogen content than specimens taken directly from the 

 intestine (Morita, 1938). Starvation experiments have 

 not yet been performed with any intestinal amoeba. Eeal 

 progress in the study of the metabolism of these organ- 

 isms will only be possible when they can be cultured under 

 sterile conditions. 



