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THE AMEBIC AN NATURALIST 



[Vol. L 



salts. This closely resembles that of fresh-water fishes. 

 The blood of mammals contains a slight increase in its 

 saline content. Bunge ( J 89) states that human blood 

 serum contains about 0.84 per cent, to 0.86 per cent, salts. 

 Macallum ( '10) calculating from Abderhalden's analyses, 

 concluded the total saline content of the blood of the dog 

 amounted to 0.935 per cent., that of the cat to 0.933 per 

 cent, and that of the sheep to 0.905 per cent. To quote 

 from Macallum : 



In mammals, according to Abderhalden's analyses, there is an extraor- 

 dinary similarity in the inorganic composition of the serum of the num- 

 ber of the forms taken and the ratios of the sodium, potassium, calcium, 

 and magnesium are almost parallel with those in the Teleosts and 

 Elasmobranchs. 



Macallum had an opportunity to analyze the blood of 

 "the whale common in the Pacific off the coast of British 

 Columbia," and the parallelism between the inorganic 

 constituents of its blood and that of the horse and pig was 

 remarkable, thus bringing the whales very close to the 

 Ungulates to which some anatomists relate them. 



The above studies of the osmotic pressures of the blood, 

 the change in the permeability of the protecting mem- 

 branes and the inorganic and organic composition of the 

 blood are understood only by viewing them from the 

 standpoint of evolution. The increase in saline content 

 of mammalian blood as compared with amphibian and 

 fresh-water teleosts can be ascribed to the regulative ac- 

 tion of the kidney. Most investigators give the impres- 

 sion that the osmotic pressure of the blood of animals is 

 definite and fixed. This is not true. Findlay calls at- 

 tention to the variation in the osmotic pressure of human 

 blood at different times of day. For example, a distinct 

 though slight rise (0.03°) is noted after meals. This 

 question needs further study. My investigations showed 

 that Mustelus canis can pass with entire safety through a 

 range of 0.15° (+ and- ) in its osmotic pressure. The 

 range through which invertebrates can pass is much 

 greater. The observations of Dekhuyzen ( '05) and Dakin 

 ('08) show that the range becomes limited in the case of 



