616 Prof. Macallum. Inorganic Composition of the [June 23, 



-of the sea water from which the examples of the cod were taken was — 1'80°.* 

 The blood in Elasmobranchs thus has an osmotic pressure approximately like 

 that of sea water, while in Teleosts it is much less, in fact, only in excess of 

 •one-third. Dekhuyzen's observations would show that there is a tendency 

 in the blood of Teleosts to increase the osmotic pressure with the increase in 

 the saline concentration of the sea water, but it does not in Gadus morrhim 

 pass beyond the limit of —0-811° C. The sea water thus influences only 

 to a limited extent the osmotic pressure in Teleosts, while it has affected the 

 blood in Elasmobranchs to the extent that the A is the same as or greater than 

 it is in sea water. This balancing of the sea water and the blood plasma 

 postulates an association with the sea for Elasmobranchs, which in duration 

 •exceeds enormously the time which has elapsed since the Teleosts arose. 

 Strutt,t basing his observations on the amount of helium enclosed in a sample 

 of ha;matite fl'om the Eocene and on the amount of this gas liberated in a 

 measured time from a certain quantity of uranium, suggests that about 

 30,000,000 years have passed since the Eocene. What then must have 

 been the length of the interval between the Silurian and the present 

 in order to account for the development of the high osmotic pressure in 

 Elasmobranchs ? 



The difference between the A of the serum ( — 2'035°) and that due to the 

 salts in it ( — 1-0737°) depends on urea and other organic solutes. Urea is 

 present in large quantities in the blood of the Elasmobranchs. The first to 

 note its presence in extraordinarily large amounts (" colossale Quantitaten "), 

 mot only in the blood but also in the nniscles, liver, kidney, spleen, pancreas, 

 ■ovaries, and testes of these animals were Staedeler and Frerichs,J who 

 ■obtained as much as two ounces from the liver of a single shark {Scyllium 

 ■canicula). Later, in 1890, von Schroeder§ found that in Scyllium cat id us the 

 blood as a whole had 2'6 per cent. urea. Assuming that the blood corpuscles 

 were free from urea, the latter, he calculated, would constitute 31 per cent, of 

 the plasma. In the liver and muscles of this animal it amounted to 1"36 and 

 1"95 per cent, respectively. llodicr|| also noted that one-third oi the osmotic 

 pressure of the blood of sharks is due to urea. As the A which he found in 

 ihe blood of all the forms he exaniined amounted to — 2*05°, as much as 



* Tlie A of tlie nen water of the Atlantic along the coast of Nova Scotia and New 

 Brunswick would seem not to exceed — 1*90\ 'I'he sea water of t'anso, the most eastern 

 point of Nova Scotia, f,'ave - \'82b" and the niaxinnun value for the sea water at 

 at. Andrews, New Urunswick, was - 1 •H.'i '. 9 



t ' Roy. Soc. Pror.,' A, 1910, vol. 83, ]>. !)(!. 



I 'Journ. fiir Pract. ('hem.,' \ Hr>H. vol. 7:$, )). 48. 



§ 'Zeit. fiir Physiol. Clicm.,' IH!)(i, vol. 11. p. :u(i.- 



Jl 'Travati.x des Lab. Soc. Scientif. et Station Zool. d'Ai^cachon,' 180!), ]). lO:?. 



