ANAEROBIC METABOLISM 221 



In general, decarboxylation and deamination seem to 

 liberate but little energy. These processes will, how- 

 ever, be of the greatest importance in transforming for- 

 eign protein into the specific protein of a given organism. 

 On the other hand, as Stephenson (1939) remarks, the 

 reaction (h) which releases hydrogen, "may perhaps be 

 regarded as an anaerobic device for obtaining energy 

 from amino acids without the use of oxygen or a hy- 

 drogen acceptor." But it is not yet known whether it 

 occurs in invertebrates. 



It has already been stated that our knowledge con- 

 cerning the anaerobic protein metabolism of inverte- 

 brates is extremely scanty. The investigations perform- 

 ed so far have not gone beyond the identification of some 

 end products, and even this was done only in a few iso- 

 lated cases. It would therefore be premature to try to 

 develop a general picture of anaerobic protein degrada- 

 tion. We can only present a brief review of the various 

 papers that shed some light on the question. 



Geimann (1936) observed that the ammonia content of 

 the muscles of the medusa Aurelia aurita increases if the 

 animal is kept for 2^/2 hours under anaerobic condi- 

 tions. 



Ammonia is also the most important identified water- 

 soluble, nitrogenous end product of the anaerobic me- 

 tabolism of Ascarls. About one-third of the excretevi 

 nitrogen is present in the form of ammonia; the other 

 two-thirds can be precipitated with phosphotungstic 

 acid and are obviously a mixture of various substances 

 (Weinland, 1904a). Besides ammonia small amounts of 

 amine bases, unidentified substances giving the biuret 

 reaction, hydrogen sulfide and mercaptan are eliminated 

 (Flury, 1912; Kiiiger, 1936). Urea, on the other hand, 

 seems not to be formed by this worm (Chitwood, 1938). 



The nitrogenous end products of the anaerobic metab- 

 olism of flukes are still less known. This is due to the 



