624 E. SCHOFFENIELS 



As shown in Table II the extent of the inhibition is very different 

 depending on whether we consider the colon or the intestine. This could 

 be explained by a very high passive permeability to Na in the intestine. 



TABLE III 



Effect of Na and K Concentrations on the Potential Difference across 



THE Isolated Epithelium of the Colon and the Small Intestine in the 



Turtle Testudo Jientionni G. G. Gmelin 



M = mucosal side; S — serosal side. Potential difference in mV; the sign refers 

 to the serosal side. Explanations in the text. 



RS04 



RS04-Na/io 

 RSOj-Na/io-K 10 



RSO4 

 RSO4 

 RSO4 



RSO4 



RSG.-Na/io 



RS04-Na/io-K;- 10 



RSO4 

 RSO4 

 RSO4 



RSO4 

 RSO4 

 RSO4 



RSO. 



RSO.-Na/io 



RS04-Xa/io-K 10 



RSO, 

 RSO, 

 RSO, 



RSO4 



RSO,-Na/io 



RS04-Na/io-K • 10 



57 

 48 

 48 



Let us consider now the effects of a modification in Na and K concen- 

 trations on the potential difference across both intestine and colon (Table 

 III). In these experiments CI is generally replaced by an equivalent amount 

 of the non-penetrating anion SO4. When Na or K are removed, they are 

 replaced by an iso-osmotic amount of sucrose. RCl means a physiological 



