PEOFESSOE MATTErCCl’S ELECTEO-PHYSIOLOGICAL EESEAECIIES. 
137 
muscle begins to be convulsed, the needle is deflected through the zero-point, and is 
seen to oscillate on the negative side of the zero, until the contracting power of the 
muscle is exhausted, which always happens before the needle has had time to come to 
rest* * * § .” This fact, which M. Du Bois Eeymond has analysed with much care, is inter- 
preted by him in the following manner, which, for the sake of greater exactitude, we 
give in the words of the above-cited abstract, which are in accordance with the opinion 
repeatedly expressed by the author himself in his original workf At first it might 
be supposed that this showed a current during the tetanus in a direction contrary to that 
dm’iug rest ; but this is not the case. Before the tetanus begins, the secondary polarity 
is evolved on the platinum plates in the conducting vessel. This polarity tends to pro- 
duce a current in the opposite direction to the muscular current. As soon, then, as the 
muscular current, in consequence of the tetanus, diminishes to a certain degree, the 
current of the secondary polarity becomes the more powerful, and the needle is instantly 
defiected to the negative side;|;.” M. Du Bois Keymond evidently admits that the elec- 
tromotive power of a muscle decreases in the act of contraction, which is equivalent to 
saying that in all cases of induced contraction, considered as owing to a negative variation 
of the muscular current, as well as in all his experiments of this kind made mth the 
galvanometer, the muscular current ought necessarily to circulate previously either in 
the neiwe of the galvanoscopic frog, or in the wire of the galvanometer. 
I can only refer here to the descriptions of experiments contained in the Ninth Series 
of my Researches on Electro-physiology §, several of which prove very clearly that induced 
contraction is obtained in conditions in which the previous circulation of the muscular 
current cannot be verified. 
On the other hand, I was thus impelled to redouble my efibrts to arrive at a clear idea 
of the phenomena of induced contraction, and I feel satisfied in being now enabled to say 
that I have at length succeeded in attaining my object. I shall be as concise as possible 
in describing the three principal experiments on which my last conclusions are founded. 
It is not necessary that the galvanometer employed in these experiments should be 
the most delicate, that is, of 24,000 cods, an ordinary one of 1500 or 2000 coils being 
sufficient for the pm’pose. The metallic plates with which the circuit is closed should be 
of zinc, perfectly well amalgamated, that is, recently immersed in diluted sulphuric acid, 
then in pure mercury, and afterwards washed repeatedly in water. The two plates thus 
prepared, plunge in a saturated and neutralized solution of sulphate of zinc contained, 
as before described, in two small glasses, provided with strips or cushions of paper or 
flannel wEich imbibe the liquid in the manner adopted by M. Du Bois Reymond. If 
* “ On Animal Electricity,” Abstract of tbe Discoveries of Emil Du Bois Ebtmoxd; edited by Dr. Bexcs 
Jones, p. 132. 
t Dntersuchungen iiber thieriscbe Electricitat. 
X “ On Animal Electricity,” Abstract of tbe Discoveries of AImil Du Bois Eetmond ; edited by Dr. Bence 
Jones, p. 134. 
§ Philosopbical Transactions, 1850. 
MDCCCLVII. U 
