H. P. WOLVEKAMP 



the edible crab and the snail. The fact that the/?H of the blood of these 

 animals is higher than 8 when in equilibrium with atmospheric air, 

 whilst the isoelectric point of haemocyanin lies between pH 4-7 and 

 pH 5-2, would seem to favour the formation of this compound. This 

 seems, however, not to be so for in collaboration with Kruyt 15 1 found 

 with the method of Stadie and O'Brien 16 that the amount of C0 2 

 quickly absorbed by the blood of the snail, the crab and the lobster 

 does not surpass the quantities absorbed by water (Figure 8). 



A comparison between the content of different amino acids in 

 haemoglobin and in haemocyanin does not reveal as far as I can see 

 very striking differences that would account for the absence of carbamate 

 formation. 



Table I. Content of Some Amino Acids in Round 

 Numbers, based on a Table of Roche 



Roche 3 from titration curves of haemocyanin of five species — amongst 

 them the edible snail — confers to the haemocyanin the three pK 

 values 6-6-7-0, 7-8-8-4 and ± 10-5. 



As, however, the interpretation of those pK values in relation to 

 the fact of the direct combination of C0 2 with the blood pigment has 

 led in haemoglobin to controversies which are not yet solved 

 (v. Roughton 17 ), I do not think it advisable at the present to try to 

 deduce any explanation, from these pK values and the table of amino 

 acid contents, of the absence of direct binding of C0 2 by haemocyanin. 



I should have preferred to present more well established facts and 

 less speculations, but at the present our data on the gas binding proper- 

 ties of the blood of molluscs and crustaceans, fragmentary as they are, 

 are still far ahead of our knowledge of their blood circulation and 

 respiration, not to speak of the respiratory conditions in the natural 

 habitat. It might be pointed out, on the other hand, that further 

 experiments on cephalopods at least look promising. 



It might also be objected that some of the gas binding properties 

 of the blood, especially of the snail, might eventually prove to have no 



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