48 



ABSORPTION AND RETENTION OF POTASSIUM 



and more important cause of variation is due to fluctuations in the 

 water content of the muscles. In a series of nineteen determinations 

 of the water in fresh (not perfused) frog muscles the minimum was 

 79.10 per cent and the maximum 82.22 per cent. Comparison of 

 these results with the previous history of the animals, season when 

 collected, duration of captivity, etc., showed no consistent correlation. 

 The variation is sufficient, however, to make it advisable, when 

 comparing the potassium content of different muscles, to determine 

 potassium as per cent of the dried weight of the muscle. The average 

 for the series was 80.78 per cent which is within the range of the 

 averages commonly given for water content of muscles of cold-blooded 

 animals. A third, and chief reason, is the actual variation in the 



TABLE I. 



Potassium Content of Fresh Normal Frog Muscle. 

 Results Are in Per Cent of Potassium in Moist Muscle as Weighed. 



potassium content of the muscles of different frogs. For example the 

 average of twelve analyses on eight frogs taken from localities in 

 Rhode Island and Massachusetts during the summer and analyzed 

 soon after collection was 1.807 per cent of potassium in the dried 

 muscle while the average of seven analyses on muscles of six frogs 

 brought from Louisiana in winter and used some months later 

 was 1.591 per cent of potassium in dried muscle. The relation of the 

 potassium content of frog muscle to reproductive activities, to sex, 

 to the food supply, and to species would be interesting. Such studies 

 have not been attempted in this work. The results indicate that a 

 prolonged stay in an aquarium without food causes a diminution of 

 potassium. The individual variations are greater than the analyti- 



