#68] 
lus upon thé nerves to which it was 
;communicated. But that this was 
not the case was, afterwards made 
evident, by the following experi- 
ments and considerations. 
1. A metal, rendered capable by 
friction of exciting contractions, 
produced no change upon Mr, Ben- 
net’s gold-leaf electrometer. 
2. The interposition of moisture 
does not, in any instance I know of, 
increase the effect of fricti:n in ex- 
citing the electric fluid.. In ’some 
instances it certainly lessens this ef- 
fect. But meistened substances, 
when rubbed; by a metal, commu- 
nicate to it the capacity of produc- 
ing contractions, much more readily 
than the same substances do when” 
dry. 
3. If my hand, from being anim- 
perfect Gincithen; had occasioned 
an accumulation of electricity in 
the metal which was rubbed, a 
greater effect of thesame kind ought 
certainly to have been produced by 
insulating the metal completely ; 
which is contrary to fact. 
4. I placed a limb of a frog, pro- 
perly prepared, upon the floor of 
my chamber ; if a severe frost bad 
“not prevailed when I made this ex- 
periment, I should have !aid it upon 
the moistened surface of the earth, 
I then raised from the muscles, by 
means of an electric, the loose end 
of the nerve,:and touched it with 
the rubbed part ofa piece of metal ; 
but no contractions followed. To 
be convinced that this was not 
owing to any want of virtue in the 
metal, I kept the same part of it still 
in contact with the nerve, while I 
applied another part to the muscles; 
immediately upon which. contrac- 
_ tions were excited. , 
5. Admitting now the limb of an 
@nimal to be in such an experiment 
ANNUAL REGISTER, 1795. 
completely insulated, and that. the 
metal actually becomes electrical 
from the friction it undergoes,surely 
a very few-applications can only be 
required to place them both in the 
same state with respect to the elec~ 
tric fluid ; and when tbis happens, 
all motions depending on the trans- > 
flux of that fluid must necessarily 
cease. I have found, howeyer, that 
a piece of metal which has been 
rubbed will excite contractions, 
alter it has been many times applied 
to the lrmb. In one instance, vigo- 
rous contractions were occasioned 
by the 200th application; and if I 
had chosen to push the experiment 
farther, I might certainly have pro- 
duced many more. I may mention 
also, as connected with this faut, 
that I have frequently obsérved 
piece of metal to excite motions, 
an entire day after it had begn 
rubbed. 
What I have said will, probably, 
be thought more than sufficient to 
prove, ‘that metals, after being 
rubbed, do not produce muscular 
contractions by means of any dis- 
engaged electricity they contain. If 
my vpinion were now asked, re- 
specting the mode in which friction 
communicates such a power to them, 
I should say, that the part which has 
been rubbed is-so far altered, in 
some condition or property, as to be 
affected differently, by the fluid ex- 
citers, from a part which has not 
been rubbed; in short, that the 
rubbed part becomes, as it were, a 
different metal. ‘There are two 
facts, besides those already men- 
tioned, which support this conjec- 
ture. The first is, that when I have 
endeavoured to give an equal degree 
of friction to the two parts of the 
metal which I applied to the muscle, 
and its nerye, little or ne motion 
was 
