ANAEROBIC HABITATS 



35 



TABLE 6 

 Gas Tension in Various Organs of Cold-blooded Vertebrates. 



Representative figures concerning the oxygen tension 

 prevailing in the tissues of vertebrates have been as- 

 sembled in Tables 5 and 6. In evaluating the signifi- 

 cance of these figures it should be kept in mind that 

 the oxygen tension of a normal atmosphere at sea level 

 is 158 mm. Hg. It is therefore conceivable that the 

 oxygen tension in the tissues of warm-blooded verte- 

 brates, with values ranging from 10 to 45 mm. Hg., is 

 low enough to influence the metabolism of at least some 

 larger parasites. 



Campbell (1931) has furthermore pointed out that in- 

 flammatory j^rocesses lower considerably the oxygen ten- 

 sion of tissues. A similar condition might well prevail 

 in cases of various pathological changes caused by the 

 presence of parasitic protozoa or helminths. This prob- 

 lem would deserve further experimentation. 



The data available for cold-blooded vertebrates show 

 that in some organisms (frogs and toads) the oxygen 

 tension of the subcutaneous tissues is somewhat higher 

 than that found in warm-blooded vertebrates but that 

 in other organisms (snakes and tortoises) it is about 

 the same. A complicating factor in the former group is 

 that the oxygen tension of these tissues seems to be de- 

 pendent on the temperature. At low temperatures the 

 oxygen tension appears to be quite high, so high, in fact, 



