When an isolated frog muscle is immersed in Ringer's solution there is a considerable interchange of electrolytes, some potassium diffusing out and some sodium and chloride diffusing in. I n attempting to strike a complete balance between anions and cations it was found that the loss of potassium (Fenn and Cobb, '34) and the gain of chloride (Fenn, Cobb and Marsh, '34) were greater in general than could be accounted for by the other cations gained and the other anions lost. I n searching for other electrolyte changes to complete the balance some measurements were undertaken of the protein and other nitrogenous compounds which were lost from the muscle, in the hope that these would help to explain the chloride gain. At the same time further data concerning the variations and time relations of the gain in chloride were obtained. The results are reported in this paper.
Time course of ndrogem loss artd chloride gairt. The procedure consisted of dissecting out the sartorius, ileofibularis, semitendinosus, tibialis anticus longus, and peroneus muscles from a sufficient number of frogs (usually two) to obtain two sets of matched muscles, each set weighing about 1 gm. These small muscles were then immersed for varying periods of time in 10 cc. of oxygenated Ringer-phosphate solution, one set for 5 hours and the other set for a shorter or longer 469