510 SCIENCE PROGRESS. 



Rosenthal soon corroborated the truth of the original 

 observation, and likewise considered that a " gland current " 

 was under observation, since he found the source of electro- 

 motive force lay nearer the outer than the inner surface of 

 the skin ; he further demonstrated that a similar ingoing 

 current could be derived from both the acid stomach and 

 the alkaline or U t in both frop- and rabbit. 



A " current of rest " of probable glandular origin having 

 been shown to exist, it was necessary to obtain evidence of 

 " current of action " as result of excitation of the nerves of 

 the skin glands. 



The first systematic research upon the subject was by 

 Roeber, under Rosenthal's direction, though it should be 

 mentioned that Valentin had seen the effect several years 

 previous. 



Roeber observed an outgoing " current of action " (i.e., 

 negative variation of the current of rest) to be the rule, 

 though the matter was complicated by the occasional 

 appearance of an ingoing current. The effect was not 

 affected by curare ; indeed, his most striking experiment 

 was with a curarised and subsequently strychnised frog, 

 in which a tap on the table sent the galvanometer needle 

 into "Zuckungen," while the frog lay motionless. 



The matter shortly became the subject of a masterly 

 research by Engelmann. Having made an exhaustive 

 microscopic examination of the glands of the skin and 

 membrana nictitans in the living state, paying especial atten- 

 tion to the conditions of the contractile phenomena first 

 described by Ascherson, Engelmann turned his attention to 

 the electrical changes. Imbued at the time with the " Pra- 

 existenz Theorie " of Du Bois-Reymond, for Engelmann 

 the current of the " resting " skin derived its electromotive 

 force from the fibres of the contractile sheath of the glands, 

 and this electromotive force he considered as the " Trieb- 



current running in the gland from neck to base, i.e., neck galvanometrically 

 negative to base ; so also in a unicellular gland (goblet cell) current from 

 superficial to deep end of the cell. Outgoing has, of course, the opposite 

 meaning. The adoption of these expressions saves to a large extent the 

 confusion liable to arise from the use of the terms " negative or positive 

 variation ". 



