ELECTROMOTIVE PHENOMENA IN GLANDS. 511 



kraft " for the passage of fluid across the living cells in an 

 act of secretion. 



Says Engelmann : " Die Absonderung der Hautdriisen 

 ist nichts Anderes als electrische Osmose ". 



The " negative variation " of the "current of rest" of 

 the skin, upon excitation of its nerves, he considered as due 

 to the " negative variation " of the pre-existing current of 

 the contractile cells. Thus the forcing of fluid into the 

 lumen of the gland was considered as taking place con- 

 tinuously, while at intervals, when the outer sheath con- 

 tracted, expulsion of the contents of the lumen took place, 

 and for the time being the " Triebkraft " was diminished. 

 Engelmann, indeed, always obtained the highest readings 

 for the electromotive force of the " current of rest," under 

 conditions which he knew from microscopic work to be 

 favourable to dilated glands with resting "muscle" sheath. 

 Later, direct observations upon the electromotive force of 

 smooth muscle fibres from the stomach of the frog seem to 

 have raised doubts in Engelmann's mind as to the validity 

 of his original " myogenic hypothesis," and the idea is 

 noted here rather for its ingenuity and historical interest 

 than for any other purpose. The actual observations are, 

 however, in many respects of great value, and it should be 

 noted here that Engelmann observed something of the 

 nature of a " double current " (outgoing followed by ingoing) 

 upon excitation, though he considered the second effect as 

 of the nature of an " after effect ". 



Hermann next studied the subject. In his first paper 

 he does not commit himself to any definite explanation of 

 the source of electromotive force of the "resting" skin, 

 though on the idea that sonie cell processes may underlie 

 the matter, he hints at some difference of action in the 

 mucous and granular varieties of skin glands being the 

 cause of the diphasic . variation, which he also observed. 

 The normal direction of the "current of action " is, accord- 

 ing to Hermann, ingoing, though there is often a preceding 

 outgoing "Vorschlag". This statement is quite opposed 

 to the finding of Engelmann, who, as a rule, got outgoing 

 action current on stimulation. 



35 



