No. 599] OSMOTIC PRESSURE OF THE BLOOD 



657 



dition is lacking in the marine invertebrate. Some one 

 has characterized the jellyfish as organized sea water. 

 According to Macallum the blood of Limulus is but 

 slightly modified sea water. The blood of the marine in- 

 vertebrate has remained at the same low level so far as 

 the presence of nitrogenous compounds is concerned. To 

 what may we ascribe this new condition? Is it due to 

 great proportion of nitrogenous food? To the partic- 

 ular kind of liver? To the great development of the mus- 

 cular system? To a peculiar function of the kidney? 

 Questions can at present be asked only. We lack infor- 

 mation as to certain aspects of elasmobranch physiology. 



However much the elasmobranch may have experi- 

 mented in the matter of unique nitrogenous content of the 

 blood, it is certain that this condition is lacking in the 

 teleosts. And the lack there is carried over to the forms 

 which developed further. For the osmotic pressure of 

 the blood of teleosts is again determined almost wholly 

 by the salts present. The salt content of the blood of 

 marine teleosts is considerably less than that of elasmo- 

 branchs. Quinton ( '00) found the blood of eight species 

 of marine teleosts to contain 1.076 per cent, salts. Rodier 

 ( '99) found that the blood of the ganoid, Acipenser sturio, 

 had a salt content varying from 0.643 per cent, to 0.979 

 per cent. The blood of Lophius, a strictly marine form, 

 contained 1.164 per cent, salts. * Hamburger states that 

 teleost blood contains 0.936 per cent, salts, but whether 

 these are fresh-water or marine species is not stated. 

 Macallum ('10) found that the blood of the cod, Gadus 

 callarias, contained 1.2823 per cent., while that of the pol- 

 lock, Pollachius virens, contained 1.2934 per cent, salts. 

 It is evident, therefore, that the percentage of salts in the 

 blood of the marine teleost has been decreased as com- 

 pared with the total saline content of elasmobranch blood. 

 Moreover, the osmotic pressure of the blood of the teleost 

 is due almost wholly to the salts present. Macallum ( M0) 

 proved this. He found that the A of the salts of cod blood 

 was 0.71°, while that of the entire blood was 0.765°. 



