462 ELECTRO-PHYSIOLOGY CHAP. 



the development of muscle and nerve physics, although some 

 fundamental researches date as far back as the discovery of the 

 muscle current. 



There was for long a certain disinclination to attribute 

 electromotive activity to cells of which a regular mole- 

 cular structure, comparable with that of muscle, could not be 

 predicated. Engelmann (72) in 18*72, during a discussion as 

 to whether the electromotive action of the frog's skin should 

 be referred to the glandular epithelium, expressed his reluctance 

 " to assume in cells which, like those before us, exhibit no sign 

 of regular, axial arrangement of the particles, any regular, 

 electromotive structure capable of giving external visible 

 response," and maintained that the gl&ud-mitscles were the sole 

 effectual source of the electrical currents within the glandular 

 layer. 



As we have seen, du Bois-Eeymond, whose name once 

 more heads these investigations, was led by his attempts to 

 demonstrate the supposed current of rest in uninjured muscles 

 in situ through the skin, to the discovery of the marked electro- 

 motive activity of the frog's skin. On bringing any two points 

 of the uninjured surface of a piece of excised skin, stretched on a 

 glass plate, with leading -off pads of salt clay, into unequal 

 contact, he always obtained a current which flowed within the 

 skin from the pad last applied to the other. When both pads 

 were applied as nearly as possible simultaneously, the needle 

 remained at rest comparatively speaking. 



Du Bois-Eeymond at once recognised that this effect was pro- 

 duced by the non-simultaneous contact. " Each point of contact 

 is the seat of electromotive force in the direction of pad to skin, i.e. 

 inwards ; but the contact of the salt solution acts at the same time 

 upon the cause of the electrical impulse. Hence, with dissimilar 

 contact, there is a current in the direction of impulse from the last 

 point of contact, which continues until the difference in impulse 

 at the two points becomes negligible." Du Bois-Eeymond 

 next obtained much stronger deflections on leading off from the 

 external and internal skin surface, always indeed in the direction 

 from the former to the latter. Here, too, the impulse was soon 

 abolished by salt solution, and was ab initio nil when the 

 surface of the skin was painted with Nad before leading off 

 from it. The current was equally neutralised by scraping off the 



