1 96 .SOURCES OF ENERGY IN ANAER0BI08IS 



however, the sapropelic ciliates seem to be truly anaero- 

 bic animals, i.e., they are injured by molecular oxygen. 



A well-developed anaerobic protein metabolism is en- 

 countered in Hirudo medicinalis (Laf argue and Faye- 

 mendy, 1932a; Braconnier-Fayemendy, 1933). One hun- 

 dred grams of leeches excrete, according to Braconnier- 

 Fayemendy, from 7 to 9 milligrams of non-protein nitro- 

 gen in 24 hours under anaerobic conditions. The author 

 speaks of an enormous drop in the total nitrogenous ex- 

 cretion C'une baisse enorme") under anaerobic as com- 

 pared to aerobic conditions, and she lists this excretion 

 as amounting to 17 to 19 mg. A study of her tables, how- 

 ever, indicates that this figure is obtained in 48-hour pe- 

 riods. Either, therefore, the caption of the table is er- 

 roneous, or her above statement is unwarranted. A clar- 

 ification of this point through further experiments is de- 

 sirable, since so little is known about the anaerobic pro- 

 tein metabolism of any invertebrate and since leeches 

 are probably one of the best objects for such a study. 



There seems to be a certain difference in the signifi- 

 cance of protein metabolism in Hirudo and in parasitic 

 worms. In Hirudo the nitrogenous end products result, 

 in all probability, from a tj^pical energy-liberating mech- 

 anism. In the parasitic worms, on the contrary, in which, 

 as was mentioned above, large quantities of reproductive 

 cells are released during anaerobiosis, a large part of the 

 soluble nitrogenous excreta probably originate from proc- 

 esses which lead to the formation of these cells, and 

 which would then have no connection with energy pro- 

 duction. — For quantitative data the reader is referred to 

 the papers of Weinland (1904a), Weinland and von 

 Brand (1926) and von Brand (1933a; 1934a).— It is 

 possible, however, that Ascaris derives some energy from 

 an anaerobic protein metabolism. According to Schulte 's 

 (1917) observations only 80 per cent of the heat pro- 

 duced by the worms can be ascribed to carbohydrate 



