100 



THE PHYSIOLOGY OF EARTHWORMS 



little if any of the oxygen uptake and transport in L. terrestris was 

 carried out by haemoglobin. The affinity of haemoglobin for 

 oxygen is outweighed only by its affinity for carbon monoxide. In 

 combining with carbon monoxide the amount of haemoglobin 

 available for reaction with oxygen is reduced. By adding carbon 

 monoxide to gas mixtures it is possible to investigate the efficiency 

 of haemoglobin systems. Johnson (1942) in fact used mixtures of 

 carbon monoxide and oxygen, having sufficient CO to saturate 



40 80 



Partial pressure of oxygen, 



mm Hg 



Fig. 31. Mean rate of oxygen consumption of earthworms at 



10 °C at different oxygen pressures. A, during first hour in absence 



of CO ; Bi during second hour in absence of CO ; B2 during second 



hour in presence of CO (from Johnson, 1942). 



95 % of the haemoglobin of the blood of Lumbricus. The oxygen 

 consumption of carbon monoxide treated animals is significantly 

 lower than that of untreated animals at all oxygen pressures 

 down to 8 mm Hg but not at this partial pressure (Table 14, 

 Fig. 31). 



In order to check that this depression of oxygen consumption 

 was indeed due to inhibition of haemoglobin, Johnson (1942) 

 studied the respiratory rate of tissue slices (of the body wall) in the 

 presence of CO, and found that the oxygen uptake of CO treated 

 slices was 110% that of untreated slices. There was no decrease in 



