TRAXSITIOX TO ANAER0BI08IS 145 



cliin or a starfish has no known mechanisms for regulating 

 the respiratory surface. It would be of considerable in- 

 terest to compare the rates of oxygen consumption of such 

 animals when fed and when unfed, or to test whether sub- 

 stances, like dinitrophenol, which increase the rate of 

 oxidations in many animals, have any effect on them. 

 The results obtained might elucidate the theory of the 

 limiting action of diffusion. 



But why the circulatory system of Helix, for example, 

 or that of Callinectes and Homarus should not be effi- 

 cient enough to provide all the tissues with oxygen at 

 moderate tensions is by no means obvious. More baf- 

 fling still is the question why the oxygen consumption 

 of the small Spirostomum should be dependent on the 

 tension. It is a case that would merit reinvestigation 

 from various angles. 



Gerard (1931), who presents a mathematical treatment 

 of the oxygen diffusion into unicellular organisms at 

 various tensions, points out that the assumption of a 

 uniform diffusion throughout the cell is probably an over- 

 simplification. The phenomenon may be complicated by 

 different diffusion constants and the respiratory rate 

 may not be uniform in all zones of a given cell. 



One should also take into account the observations of 

 Kemi^ner (1937) who showed that, for a variety of bio- 

 logical objects, the effect of oxygen tension on cellular 

 respiration is definitely influenced by factors like pH, 

 carbon dioxide tension, salt content or temperature. 



Thus it is questionable whether the above division into 

 two groups is justified. This has been emphasized re- 

 cently by Maloeuf (1937) whose views have also been 

 accepted by von Buddenbrock (1939). Their argumen- 

 tation is that, if one lowers the tension gradually, a point 

 will be reached where, in all animals, the oxygen con- 

 sumption will decline. In other words, the difference 

 between various animals consists only in the position of 



