622 



E. SCHOFFENIELS 



The potential difference is measured on isolated segment using the method 

 of Wilson and Wiseman [i] or a new method described elsewhere [2]. In 

 the latter case, the fragment of organ is opened flat and mounted between 

 two chambers. When anatomically possible, the muscle layers are stripped 

 off the epithelium. 



It can be seen (Table I) that: 



(a) the lumen of the digestive tract is negative with respect to the 

 serosal fluid, 



TABLE I 



Potential Difference across the Epithelium of the Digestive Tract 

 IN Various Animal Species 



The potential difference is recorded on isolated preparations : isolated sac (A) 

 or method of Baillien and Schoffeniels [2] (B) with (S) or without stripping of the 

 muscle layers. Both sides of the preparation are bathed with physiological saline. 

 The sign refers to the serosal fluid. 



Terrestrial turtle 



{Testudu herynanni d. P. Gmelin) 



BS 



Water turtle 



(Emvs orbicularis L.) 



small intestine 

 colon 



I -5-2 -5 

 12-20 



BS 



Frog 



{Rana tempororia L.) 



gastric mucosa 

 rectum 



30-50 

 10-50 



BS 



