26 CHARLES F. W. McCLUEE 



The left skin glove of the same frog (exper. 465, fig. 10), 

 also with the inside of the skin turned outward, was filled with 

 a 5 per cent solution of formaldehyde made up with Ringer's 

 solution approximately isotonic with frog's blood, and was 

 suspended in this same solution at 15 C. and 25 C. In this 

 case, after the initial gain in weight which occurred during 

 the first hour's suspension, the glove did not, like the control 

 (465A), lose weight continuously when placed alternately in 

 the solution at different temperatures; but between the sec- 

 ond and the sixth hours of the experiment it lost weight at 

 25 C. and gained weight at 15 C. 



While we are here undoubtedly dealing with dead skins, 

 since the latter have been immersed in a formaldehyde solu- 

 tion, nevertheless the behavior of such skins emphasizes the 

 probability that the corresponding fluctuations in weight ob- 

 served in the living frog (fig. 5) and in skins removed from 

 the body are for the most part due to the fact that the power 

 of the skins to transport water through them continuously 

 in opposition to osmotic pressure has been either greatly 

 diminished or entirely destroyed. Such fluctuations in weight 

 would therefore appear to be due to a gain or a loss of water 

 by the skin itself. These fluctuations in weight of the skins 

 are suggestive of the auxographic records made by MacDou- 

 gal 7 on the succulent leaves of Mesenbryanthemum ; these 

 showed that the growing leaves of this plant lost water when 

 exposed to high and gained water when exposed to low 

 temperature. 



Up to this point we have seen that the behavior of skin 

 gloves, when filled with Ringer's solution approximately iso- 

 tonic with frog's blood and suspended in the same solution, 

 may be the resultant of the action or the interaction of sev- 

 eral separate factors which may operate in harmony with 

 or in opposition to one another. These factors are the power 

 of the skin to absorb water, to release water, and to transport 

 water through itself continuously in a direction in opposition 



7 MaeDougal, D. T. 1920 Hydration and growth. Carnegie Institution of 

 Washington. 



