THREE FIGURES
Recent studies (Adolph, '25, '34; Luck6 and McCutcheon, '32) on the passage of materials across living membranes have made it important to know with some accuracy the quantitative values for the transfer of water across frog skin.
Since the fundamental work of Durig ( 'Ol), it has been known that frogs maintain their normal weight in NaCl solutions of less than 0.003 M, but that they gain weight initially in other hypotonic solutions, and lose weight initially in hypertonic solutions. Attempts have been made to correlate this transfer of water with the potentials existing across the skin membrane, and other attempts have been made to explain this transfer without reference to the potentials, which are then considered rather as by-products of cellular metabolism. Adolph ('34) and others have presented some evidence in favor of the view that the skin potential as such is a factor. Of this and the second hypothesis more will be said in the discussion. This paper reports the data and conclusions of an investigation pointing to surface and secretory activity, as yet unanalyeed, as among the chief factors. TECHNIQUE a. On single frogs: Frogs were kept in tap water in the laboratory for 2 days to allow them to come to equilibrium. The urine of each frog was then expressed, the cloaca tied National Research Council Fellow in Medicine. a5 JODRNAL OF CELLULAB AND COMPAFATlVl3 PHYSIOMQY, YOL. 6, NO. 1 B. B. RUBENSTEIN TIME HOUR8 I N
off with cat gut, and each frog was placed in a small coarse wire cage, the tare weight of which was known. Each frog was weighed in its cage after being allowed to drain for 2 minutes. The frogs were then immersed with their heads above the level of the test solution. The frogs were then weighed at stated intervals. At the end of the experiment, they were again weighed as before, but after this weighing TABLE 1 Typical protoeo& u h g single frog8 in cages ~ WEIQHT IN QBAYS OF SW3Q PLUS CAQE IN CAQE NUMBER AS GIVEN. CLOACAE TIED Frogs in 0.03N NaCl solution Frogs in diluted Ringer sol.