PEOrESSOE MATTErCCl’S ELECTEO-PHYSIOLOGICAL EESEAECHES. 
139 
was deflected flrst in the opposite direction, and that deflection was certainly not inferior 
to the one in the second case. 
Since no secondary polarity can interfere in these experiments (Exp. 1), they prove, 
that in the act of the contraction of these muscles, an electrical current, which, from its 
instantaneousness, I shall call electrical discharge, takes place, which circulates in the 
external conducting arc in a direction contrary to that of the muscular current. 
Exp. 3. I make a small incision in the upper part of the thigh of a frog, in order to 
lay open the inside of the muscle : it is easy to understand, that, on closing the circuit with 
the two extremities of this thigh, the current, which in this case is differential, is null, 
or is in an opposite direction to that of the usual cmnent of the thigh. The needle 
having been allowed to come to rest, and the usual contractions excited, the deflection 
which is obtained is always in the same direction, that is, opposed in the external arc to 
the usual current of the thigh when it has not been cut. Hence, if the needle is 
deflected at the beginning by the predominant current due to the transverse section of 
the upper part of the thigh, the deflection increases rapidly during the contractions. 
Finally, the experiment may be made by putting the two thighs of a frog into the 
ch’cuit, touching the imder extremities of the thighs, but leaving, nevertheless, only one 
of the lumbar nerves. The cuiTent which is obtained on closing the circuit is in no fixed 
direction, being either null, or now in the direction of one of the thighs, now in that of 
the other. In all cases during contraction of the thigh provided with its nerve, the 
usual deflection occurs, that is owing to the current chculating in the external arc of the 
muscle from the inferior towards the superior extremity of that muscle. 
I shall now add a few brief observations, which may throw further hght on the inter- 
pretation of these experiments. I need not stay to prove that the effects observed by 
means of the galvanometer, produced by a muscle in contraction, cannot depend either 
on a portion of the current employed to irritate the nerve, or on changes of contact 
between the muscle and the extremities of the galvanometer, or Anally, on the variable 
resistance of a muscle in contraction ; these doubts have aheady been completely removed 
by the experiments of M. Du Bois Retmond. In endeavouring to understand the natm'e 
of the electrical phenomena which occur in a muscle during contraction, the fact which 
merits om’ chief attention is, that the needle of the galvanometer, which deflects at flrst 
in the direction of the muscular cm’rent of the gastrocnemius, or of the enthe thigh, 
descends rapidly to zero at the moment of contraction and remains deflected in an oppo- 
site direction to that of the muscular current, during the whole time that the contrac- 
tions are frequent and powerful. M. Pouillet, in his remarkable report *, gives a lucid 
resume of the conclusions at which M. Du Bois Reymond arrived, in the folloudng terms : 
— “ D apres les principes de M. Du Bois Reymond I’effet d’une contraction soutenue n’est 
pas de faire naitre un courant, mais d’afiaiblir et de suspendre par intermittance un cou- 
rant qui pre-existait ; il faut done un com'ant pre-existant, ou il en faut deux qui soient 
egaux et opposes et qui se neutralisent,” &c. &c. The slightest reflection on the three 
* Comptes Eendua, t. xxxi. p. 28. 
u 2 
