H. E. DAVENPORT 



haemoglobin under the same conditions. The results of these ex- 

 periments showed that, with an experimental error of 5 per cent in 

 the method of measurement, equal increments of oxygen evolved 

 produced equal increments of oxyhaemoglobin concentration up to 

 complete saturation. The oxygen affinity of the Ascaris haemoglobins 

 is therefore too great for the equilibrium curve to be measured within 

 the limits of an experimental error of this magnitude. 



In view of this extremely high oxygen affinity it is necessary to 

 know, before possible functions of the haemoglobins can be suggested, 

 whether the bound oxygen is available to the oxidative enzyme 

 systems of the parasite. It was found, by experiments in which 

 worms were subjected to anaerobic conditions, that a slow deoxy- 

 genation of the body wall haemoglobin occurs. No evidence was 

 obtained for a similar deoxygenation of the perienteric fluid haemo- 

 globin. It is therefore possible that the body wall haemoglobin acts 

 as a short period store of oxygen available in conditions of extreme 

 oxygen deficiency. The evidence for this is not, however, strong. 



A haemoglobin having properties closely resembling those of the 

 perienteric fluid haemoglobin of Ascaris has been observed in the 

 perienteric fluid of Strongylus spp., intestinal parasites of the horse. 

 The deep red colour of these worms, commonly known as ' blood 

 worms ', is due to high concentrations of this pigment. The aberrant 

 properties of the Ascaris haemoglobins are not, however, shared by 

 all nematode haemoglobins. Nippostrongylus muris, a small nematode 

 parasite of the laboratory rat, contains high concentrations of a 

 haemoglobin which, under conditions of oxygen deficiency, undergoes 

 rapid deoxygenation in vivo. Extracts of the haemoglobin were found 

 to have a high oxygen affinity. In dilute solution at 19°C, pH 8-2 

 the oxygen equilibrium curve is a rectangular hyperbola and the 

 haemoglobin is half saturated with oxygen at a tension of less than 

 0-1 mm Hg, compared with 0-7 mm Hg for similar solutions of ox 

 muscle haemoglobin. 



Received September 1948 



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