242 



M. L. BASKERVILL. 



open to objection than any experimental case where solutions 

 other than lymph and water are used on the inner and outer 

 sides, respectively, of the frog skin. 



Following are the results from several typical experiments. 

 When the inner side of the skin is against the tube and so in 

 contact with the pure salt solution, while the outer surface of 

 the skin is in contact with urea, the direction is designated as 

 "normal" and the reverse direction as "turned." 



The data in Table I. show the kind of results obtained when 

 skins from whole legs were used. The skins were turned in the 

 "normal" direction and each contained 5 cc. of the solution 

 indicated. They were washed in the respective solutions for ij 

 hours before the experiment started. Three per cent, urea 

 dissolved in the same salt solution as used on the inside of the 

 skin was employed in each case. Penetration was allowed to 

 continue three hours. 



TABLE I. 



Date of experiment 10/26/22. 



Table II. presents data typical of many experiments carried 

 out with skins in the "normal" direction over 16 mm. tubes. 

 They were washed for fifty minutes in the respective salt solutions 

 and then immersed in 5 per cent, urea dissolved in the same salt 

 solutions as used on the inside of the tube. Penetration con- 

 tinued four hours. 



Table III. gives data obtained with the skins in the reverse 

 relation, i.e., "turned," over 16 mm. tubes. The skins were 

 washed for one hour in the respective solutions before the 

 experiment started and were then immersed in 5 per cent, urea 

 dissolved in the same isotonic salt solution as was used inside 

 the tube in each case. The penetration continued five hours. 



