. Electrolytes in biological systems, incorporating papers presented at a symposium at the Marine Biological Laboratory in Woods Hole, Massachusetts, on September 8, 1954. Electrophysiology; Electrolytes; Electrolytes; Electrophysiology; Physiology, Comparative. ERNST G. HUF 207 where waler How is in tlie opposite direction. Now, if frog skin separates two solutions of different osmotic pressure, for example frog Ringer's and frog Ringer's, one will notice that outward osmosis is quite a bit faster than inward osmosis (fig. i). The phenomenon of 'one-way osmosis' is very easy to demonstrat
. Electrolytes in biological systems, incorporating papers presented at a symposium at the Marine Biological Laboratory in Woods Hole, Massachusetts, on September 8, 1954. Electrophysiology; Electrolytes; Electrolytes; Electrophysiology; Physiology, Comparative. ERNST G. HUF 207 where waler How is in tlie opposite direction. Now, if frog skin separates two solutions of different osmotic pressure, for example frog Ringer's and frog Ringer's, one will notice that outward osmosis is quite a bit faster than inward osmosis (fig. i). The phenomenon of 'one-way osmosis' is very easy to demonstrate. An argument, however, arose as to whether one should say, then, that the water permeability of the skin is smaller in the inward than in the outward direction. In an often-quoted paper by v. Hevesy, Hofer and Krogh (12), it was shown that the permeability of the skin for heavy water (D2O) in Ringer's was the same, no matter whether it penetrated from the outside or from the inside of the skin. It was felt (13) that the experiments of v. Hevesy et al. settled all arguments about 'one-way water permeability' of frog skin, simply by denying its existence. Obviously, this was not justitied. The same authors had also found Fig. I. One-way osmosis across isolated frog skin in a differential osmometer. Three consecutive ex- periments of one hour duration each, using the same piece of skin from the abdominal wall of Rana esculenta. Starting off with outward osmosis, with Ringer's on the epithelial side and 10 Ringer's on the corium side. In inward osmosis the osmotic gradient was reversed using again Ringer's and ro Ring- er's. 21°. i —+ o and o —* i indicate the direction of osmosis from the in- side —> outside and the outside —> inside, respectively (19). mm 60 / 40 / / 20 / -" • / -20 • \ \ -40 \ -60 \ 1. 0,5 1,0 0 0,5 1,0 0 0,5 Hrs. 1,0 that on the basis of equally effective molar concentration differences, osmotic flow of ordinary water is, on the a
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