1910.] Blood in Vertebrates and Invertebrates. 621 





Na. 



K. 



Ca. 



Mg. 



CI. 



Whale 



0 1805 

 0 -17859 

 0 -19974 



0-2004 

 0 1917 

 0 -2273 



0 -00646 

 0 -00485 

 0 -00364 



0 -00448 

 0 -00533 

 0 -00384 



0 -26854 

 0 -2690 

 0 -2785 



Pig 







The fact that the inorganic composition of the blood in the whale is so 

 like that of the pig* and horse strongly suggests that the inorganic composi- 

 tion of the serum is the same, although, almost as long as in the case of 

 •Gadidce, the whales have been oceanic forms. 



It would seem accordingly that in the power which the kidneys exercise of 

 regulating and rendering uniform not only the saline concentration, but also 

 the ratios of the sodium, potassium, calcium, and magnesium in the blood 

 plasma of "Vertebrates so far examined, we have to deal with an unalterable 

 function of primal importance inherited from a Protovertebrate or 

 Eovertebrate type of the Cambrian or even of the Pre-Cambrian. 



The retention of urea and ammonia salts in the blood of Elasmobranchs 

 undoubtedly developed as a result of the tendency of the blood to balance in 

 itself the osmotic pressure of the sea water. The very fact that the kidneys 

 in these forms exhibit some inertness in the elimination of urea, while they 

 are very active in the elimination of the salts, is significant. AVhat they do 

 most rigorously is the regulation of the concentration and composition of the 

 salts of the blood. The firmly fi^d physiological habit ar function must he the 

 more ancient one, and consequently the earliest function toas not the elimination 

 cf waste metaholic products, hut the reyxdation of the inorganic composition of the 

 blood. Tlie function of excreting waste products came later, and in the Elasmo- 

 branchs never acquired the fixity that characterised the function concerned in 

 excreting the salts. 



That in the Gadidce, although of marine habitat since the Jurassic, the 

 kidneys rigorously keep down the saline concentration and regulate the 

 inorganic composition of the blood, while the urea is readily eliminated, is 

 not a difficulty in the way of accepting this view. The Ganoid ancestors of 

 the Teleosts were fresh-water forms, probably throughout the latter half of 

 the Palteozoic and, at least, the first half of the Mesozoic, and during all that 

 time the conditions which would tend, as in the Elasmobranchs, to increase 

 the osmotic pressure did not occur. There was notliing, then, to work 



* The parallelism in compositiou between the blood of the whale and that of the pig 

 and horse is so close that it is of special interest in connection with the origin of the 

 Cetacea. Some anatomists relate them to the Ungnlata ; others question this on various 

 grounds. The inorganic composition of the blood would seem to bring the whales very 

 dose to the Ungulates. 



