TRAN8ITI0X TO AyAEROBIOl^IS 147 



worthy due to the fact that the oxygen which is merely 

 in solution within the animal tissues and body fluids and 

 does not take part in the oxidations has been neglected. 

 Von Buddenbrock (1939) found that the oxygen con- 

 sumption of the sea-urchin Sphaerechinus granulans rises 

 from 2.28 cc. to 7.2 cc. per hour if the animal is trans- 

 ferred for one hour from normal sea water to water hav- 

 ing an abnormally high oxygen content. This, however, 

 does not actually indicate an increased rate of oxidation 

 since, during that same time, the oxygen content of the 

 body fluid rose from 1 or 2 cc. to 10.1 cc. per liter. It is 

 clear that the experiments should be conducted over 

 longer periods in order to eliminate this source of error. 

 Longer observations on the above-mentioned sea-urchin 

 (also on Aster las, according to Meyer, 1935, and on 

 leeches, according to Ratfy, 1933) show that the oxygen 

 consumption becomes lower again later on. Where a 

 true dependency on the tension does exist, even at high 

 oxygen concentrations, the increased rate of respiration 

 will be maintained for long periods. Such is the case 

 with actinians as von Buddenbrock 's (1939) experiments 

 on Aneynonia sulcata have shown. 



2. EVIDENCE OF PARTIAL TRANSITION TO ANAEROBIC 

 METABOLISM 



1. TRANSITION CAUSED BY A LOWERING OF THE OXYGEN TENSION 



Let us now consider separately the features mentioned 

 above as furnishing a definite evidence for the existence 

 of anaerobic metabolism. 



A. Excretion or accmnulation of end products of an- 

 aerobic mctaholism. As w^ill be shown in a subsequent 

 chapter, many investigations have been made on this 

 point for completely anaerobic conditions, but hardly 

 any for low oxygen tensions. The only observation to 

 be mentioned here is that of Kriiger (1936) who found 

 that Ascaris excretes more organic acid at low than at 



