H. P. WOLVEKAMP 



brates with haemocyanin, is very low, the maximum value obtained 

 by us for Sepia being 3 per cent. This means that at comparable 

 saturation and unloading conditions the blood of Sepia transports 

 only one sixth of the quantity of oxygen transmitted by human blood. 



Further we ought to know the total quantity of blood. We can get 

 from one Sepia of half a kilo weight about 20 cm 3 blood, but it is 

 quite certain that we do not get all the blood contained in the circu- 

 latory system. There is another factor which ought to be taken into 

 account. Comparative physiologists are in the bad habit of trying 

 always to bleed their animals to the last drop, even by a lot of sucking 

 and squeezing. I feel pretty sure that in doing so a not inconsiderable 

 quantity of tissue fluid will pass over into the blood circulation and 

 be drained off as well. This source of error would more or less counter- 

 balance the first mentioned. 



Even if it is assumed that the total quantity of blood is 50 percent 

 higher than the volumes obtained by bleeding the animals, we arrive 

 at the conclusion that the quantity of blood per kg bodyweight is not 

 higher, but if anything lower than in man. The low oxygen capacity 

 must accordingly be compensated by a high circulation rate and 

 by the properties of the blood-pigment, or by one of those factors. 

 We do not know how far blood circulation may be adapted to the 

 oxygen needs of the tissues, though some regulation of the blood 

 circulation certainly occurs. On the other hand the blood leaving 

 the tissues is always completely deoxygenated. In this respect 

 the cephalopods compare unfavourably with mammals where in 

 resting condition the arterial blood delivers no more than 30 per cent 

 of its oxygen content. The rest forms a reserve upon which the tissues 

 can draw during severe exercise by means of the Bohr effect combined 

 with the opening of a great number of capillaries. In the ink-fishes the 

 only means of discharging more oxygen into the tissues would seem to 

 be a shortening of the respiratory cycle by speeding up blood circulation. 



The carbon dioxide transport by blood containing haemocyanin shows 

 some peculiarities worth mentioning. In the first place the blood does 

 not contain carbonic anhydrase as was found by M. Florkin 12 and 

 van Goor 13 . The tissues, however, contain according to Ferguson, 

 Lewis and Smith 14 and to van Goor 13 varying quantities of this 

 catalyst while the greatest activity of the enzyme is always found in 

 the gills. Probably the carbon dioxide passes into the tissues in the 

 form of carbonic acid, or bicarbonate ions together with H + ions will 

 migrate into the blood, there to be counter-balanced by available base 

 (the pW of the bloods in the absence of C0 2 lies at about 8-5). The 

 reverse process will take place in the respiratory organs. Possibly 

 complications occur in relation to ionic interchange due to osmotic 

 regulation. 



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