90 



RESPIRATORY MECHANISMS 



Fig. 51 from the review given by Florkin (1934) in which the 

 lowest heavy line represents the amount of CO2 absorbed by 

 water. It will be noted that the blood of the worm Urechis 

 absorbs by chemical combination only up to a pressure of 

 about 20 mm; above that the curve becomes parallel to the 



to 



lo 



lo 



3o 



Ho 



So 



^CO a ; '>~m Kg 



Fig. 51. C0 2 dissociation curves for different bloods compared with sea 

 water represented by lowest heavy line. 



Ray at 10.4° C 



r- h Ray at 25° C 



_. ._. ._ Mackerel 



Prionotus 



Opsanus 



Urechis (Florkin.) 



curve for water and the specific transport capacity is ex- 

 hausted. The other curves show increases in combined CO2 

 up to much higher pressures, outside the range depicted. 

 When the tension is known at which the blood of one of these 

 animals is unloaded with regard to CO2 in the respiratory 

 organ and also the tension at which CO2 is taken up in the 

 tissue the transport capacity can be read off from the curve. 

 Conversely if we know the quantities in arterial and venous 

 blood and the unloading tension we can figure out the average 

 CO2 tension obtaining in the tissues. 



