506 ELECTRO-PHYSIOLOGY CHAP. 



consider the small number of mucin- producing goblet cells in 

 the one case, and the continuous surface layer of the same in 

 the other. 



We are of opinion that the preceding observations leave no 

 doubt that the electromotive effects described in certain mucosae, 

 and in the external skin of naked amphibians and fishes, are to be 

 referred to the greater or less number of uni- and multicellular 

 secreting glands present, i.e., in the last resort, to the single cell. 



From the standpoint of the earlier theoretical account of 

 electromotive action it is evident that, as regards the ex- 

 planation of the " ingoing current of rest," no difficulty is 

 encountered. Every goblet cell, or mucous cell proper, ex- 

 hibits, as a rule, under the microscope two clearly distinguish- 

 able sections one basal, nucleated and protoplasmic the other 

 dimmed, as a rule, by a mass of granules, but on treatment with 

 reagents becoming hyaline and turgescent, i.e. exhibiting unmis- 

 takable mucin metamorphosis. It must be concluded that 

 " chemical action " in the two parts of the same cell differs not 

 only quantitatively but qualitatively also, which explains the 

 difference of potential between base and free surface, fundamental 

 to the ingoing current, if the mucin metamorphosis is admitted to 

 be a chemical process, developing pari passu with the negative 

 potential. This naturally applies as much to simple, superficially 

 extended cell aggregates (throat and cloacal mucosa, external skin 

 of many fishes) as to the cases in which there is a more or less 

 complex pitting (glandular formation) ; for it is clear that, inas- 

 much as these glands open to the exterior, part of their current 

 must be included in the lead-off, which would naturally be 

 "ingoing," like the current of the superficial mucous cells. The 

 usually higher E.M.F. of the richly glandular mucosa (tongue) 

 and frog's skin, vs. the fish's skin, consisting only of goblet cells, 

 and the throat and cloacal mucosa, may well be referred to this 

 fact ; for there is no reason to suppose that the sparsely present 

 goblet cells, still less the prickle cells of the frog's epidermis, have 

 any such important electrical action. If, as pointed out by 

 Hermann, the form of the glands in the frog's skin is but little 

 suited to give external galvanic action, on the other hand the 

 capillary layer of fluid which covers the surface of the skin under 

 normal conditions, and must be regarded mainly as a glandular 

 secretion, is directly connected with the fluid contents of the 



