6S 4 SECRETION AND ABSORPTION B Y THE SKIN 
excitation of the nerves. The strength of the stimulus, and the extent to 
which the normal ingoing " current of rest " is developed, affects the result, 
and hypotheses have been based upon both of these factors of the case. 
Hermann 1 long ago suggested the possibility of augmenting and inhibitory 
fibres to the glands, and in bis most recent publication 2 still entertains the 
idea. On the other hand, Biedermann suggests that the two sides of protoplasmic 
activity (the katabolic and anabolic) in the secretory cells are associated with 
generation of electro-motive force, causing currents in opposite directions 
in the two cases ; that the electro-motive force of the " current of rest " is 
the algebraic sum of these opposing forces at the moment ; and that the results 
of nerve excitation are related directly to the ascendancy of one or the other 
metabolic action at the time of stimulation. 
The production of an outgoing "current of action" is considered by 
Biedermann as due to the nerve excitation provoking an excess of anabolic action 
in the cell, that of an ingoing " current of action " as due to excess of katabolism, 
si i that one and the same class of nerve-fibre is supposed to produce quite 
opposite results in the cell, the effect being partly conditioned by the state of 
the balance in the cell between the two processes at the moment of excitation, 
and partly by the strength of the stimulus. He supposes that the cell process 
least developed at the time of excitation, tends to be stimulated in excess of its 
fellow, so that if the ingoing "current of rest" is weak, as a result of slight 
katabolic ascendancy, excitation tends to cause an ingoing " current of action " ; 
and, vice versa, if the ingoing " current of rest " is strong, as a result of marked 
katabolic ascendancy, the result of excitation of the cell is liable to be the 
development of an outgoing " current of action." 
Hermann objects to this, that if the electrical sign of excess of anabolism 
over katabolism is plus, the induction of such a condition must start from the 
deep ends of the cells, i.e. from the ends from which they get their pabulum 
from the blood, and excess of positivity of this end of the cell comes, so far as 
the direction of current is concerned, to the same thing as excess of negativity 
at the free end of the cell, associated by hypothesis with katabolic ascendancy, 
and should develop a current in the same direction, i.e. ingoing. 
It may also be noted in this connection, that, according to Bohlen, 3 in 
the gastric mucosa of mammals, cessation of circulation or any interference 
with blood supply tends to convert the normal ingoing into an outgoing 
" current of rest." If an outgoing current is associated with excess of anabolism 
over katabolism, it is difficult to conceive how withdrawal of blood supply can 
induce such a change. A similar complete reversal of the direction of the 
" current of rest " is obtainable in the secreting membranes of the frog and 
fish by abstraction of beat, or by narcotisation with carbonic acid gas, ether, 
or chloroform. 
A strong stimulus of a nerve trunk may, in practice, cause an outgoing 
action current, and a weak stimulus one that is ingoing, but it is again difficult 
to conceive that difference in the strength of stimulus of one class of nerve- 
fibre can alter the whole character of the metabolism in the cells. 
Hermann was at one time of opinion that the two kinds of glands in the 
frog's skin might be associated with the two phases of the excitatory variation ; 
and the lip of the eel, which contains no club cells but only goblet cells, gives 
an outgoing " action current," while the body skin, rich in club cells and poor in 
goblets, gives an ingoing " action current " Avith the same strength of stimulus ; 4 
but since the cloacal or pharyngeal mucosa of the frog, containing only one sort 
of secretory cell, and the non-glandular crop of the winter pigeon, can give 
currents in both directions, the hypothesis is not of universal application. 
1 Arch. f. d. gcs. Physiol., Bonn, 1878, Bd. xvii. 8. 303. 
2 Ibid., 1894, Bd. lviii. S. 242. s Loc. cit. 
4 Reid and Tolputt, Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 203. 
