The Haemoglobins of Ascaris lumbricoides var suis 



criteria of Hartridge and Roughton 4 direct reaction between the 

 reducing agent and oxyhaemoglobin, if it occurs, must play an in- 

 significant part in the overall reaction, which therefore has the 

 characteristics of a deoxygenation and not of a true reduction. 

 Figure 1 illustrates the result of a typical experiment using perienteric 

 fluid haemoglobin. The time for half completion of the reaction 

 (t 50 ) is 150 sec compared with 0-008 sec for sheep haemoglobin 

 under the same conditions 4 . The reaction velocity of the body wall 

 pigment occupies an intermediate position between these extremes. 

 With a fresh preparation at 3°C, pH 6, t 50 was 80 ± 5 sec but a 

 decrease in the reaction velocity was observed in old preparations. 

 No change of this kind could be detected with perienteric fluid 

 haemoglobin and this pigment was used in the study of the effect of 

 other factors on the deoxygenation velocity. 



IOO 



20 



IOO 200 300 



Time in Seconds 



400 



Figure 1. Deoxygenation of Ascaris 



perienteric fluid oxyhaemoglobin in 



presence of Na 2 S 2 4 in vacuo. pH 6, 



20-5°C. 



A — ordinates on left. 

 B — ordinates on right. 



Hartridge and Roughton 4 have shown that the Bohr effect in the 

 oxygen equilibrium curves of mammalian blood is the result of change 

 in the dissociation velocity with change in pH. Thus with sheep 

 haemoglobin at pH 5 deoxygenation proceeds about 8 times more 

 rapidly than at pH 9. The influence of pH on the dissociation of 

 oxygen from Ascaris perienteric fluid haemoglobin was found to be 

 smaller but reversed in direction. At 20°C the reaction velocity at 



297 



