The osmotic changes in some marine animals

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Abstract
Using the thermal method of measuring vapor pressures devised by A. V. Hill, the osmotic pressures of the blood of different marine animals were determined when the animals were in sea water and when in various dilutions of this medium. The osmotic pres- sure of the blood of Maia squinado, Portunus depurator, Carcinus maenas, Portunus puber, and of Scyllium, is near that of the medium in which they live. The limit of dilution compatible with life is 3/4 for the last of these, 1/3 for Carcinus maenas, and \ for the others. Conger vulgaris maintains an osmotic pressure in its blood much higher than sea water and can stand a dilution to 1/10. All these animals are assumed to have osmotically permeable membranes, separating the blood from the external medium. Those able to stand the higher dilutions or to maintain a higher osmotic pressure in the blood are assumed to have an active living process which maintains the osmotic gradient. This living process is not the action of the kidneys.