36 CHARLES F. W. MCCLUBE 



a frog board and was alternately suspended up to the armpits 

 in a 0.9 per cent solution of NaCl at 18C. and 28C. The 

 frog (R. pipiens) was obtained from a dealer on September 

 25th. The experiment, beginning on September 26th, ex- 

 tended over a period of about twenty-one hours, during which 

 time the frog was suspended in a hypertonic saline solution. 

 When a ligated frog is suspended in a solution in this manner, 

 it is evident that no fluid can possibly enter or leave the body 

 except by passing through the integument. When frogs are 

 placed in finger-bowls containing a saline solution, fluid is 

 often taken into the intestinal canal through the oral cavity; 

 hence the method of suspending them on frog boards is essen- 

 tial to this type of experiment. 



It will be observed that during the first nine hours of its 

 suspension in the hypertonic solution (fig. 14), the ligated 

 frog lost weight continuously, except during the sixth hour, 

 when there was a slight gain. With the tenth hour, however, 

 the frog began to gain in weight, and continued to do so until 

 the close of the experiment. It is therefore seen that the 

 behavior of the living frog with ureters ligated when sus- 

 pended in a hypertonic saline solution (fig. 14) is identical 

 with that of a skin glove, with the outside of the skin turned 

 outward, when filled with Ringer's solution and suspended in 

 a hypertonic Ringer's solution (fig. 13). It is evident that 

 the loss in weight which immediately follows the suspension- 

 of the living frog in the hypertonic solution is, as in the case 

 of the skin glove, due chiefly to differences in the osmotic 

 pressure of the fluids which bathe the skin's opposite sur- 

 faces. Also, in each instance, after an equilibrium has been 

 established and water is no longer driven by osmosis 

 through the skin outward, a gain in weight of the frog and 

 of the skin glove follows, due to the existence of a force 

 which drives water inward through the skin in a direction 

 opposite to that of the driving force of osmosis. 



We know that when the living frog remains in water, water 

 is driven by osmosis through the skin into the subcutaneous 

 lymph sinuses, and that the amount of water supplied in this 



