N0.5S2] SIGNIFICANCE OF INTERNAL CONDITIONS 339 



.00138 .((0129 



Whether such a constant 2 and C0 2 content of the 

 blood of all poikilothermal animals is to be found under 

 all conditions of existence is unknown, but the coefficients 

 of absorption of oxygen and carbon dioxide at varying 

 temperatures would indicate that the carbon dioxide and 

 oxygen held in solution in the body fluids would be sub- 

 ject to change with a change in temperature. 31 In the 

 higher forms, the iron-bearing respiratory pigment, hemo- 

 globin, absorbs all the oxygen with which it combines 



