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PROFESSOR MATTE UCCl’S ELECTRO-PHYSIOLOGICAL RESEARCHES. 
times with a metallic arc. It is needless to say that the galvanoscopic frog remains 
insulated in this experiment, merely having its nerve resting upon the muscle. 
In like manner it must be observed, that in the above experiment muscles were 
employed which had ceased to contract during the discharge, so as not to have any 
induced contraction. 
It must then be admitted that, in spite of the good conductibility of a muscular 
mass, a part of the discharge always escapes to the surface of the muscle and so 
traverses the nerve of the galvanoscopic frog. 
The occurrence of this phenomenon is still more remarkable when the nerve of the 
galvanoscopic frog is placed upon a metallic surface through which the shock is 
passed. 
The phenomenon may very well be produced by passing the discharge through a 
plate of tin or gold upon which the galvanoscopic nerve is laid out ; only in this case 
we have not so many successive shocks producing contraction as with the muscular 
arc ; evidently because the jar is much more perfectly discharged through a metallic 
conductor than through the muscle. 
The next step therefore to be verified was whether a very slight discharge passed 
through a muscular mass would still excite the galvanoscopic frog to contraction, 
even when an insulating medium was interposed between the surface of the muscle 
and the galvanoscopic nerve. It also suggests itself naturally to the experimenter to 
employ in every experiment the same insulating coatings which are known to destroy 
induced contractions. 
In this view I have covered the muscular mass with a coating of turpentine, and 
laid the galvanoscopic nerve upon it. On passing very slight discharges, the galva- 
noscopic frog invariably contracts. I have repeated this experiment very frequently, 
and the only difference that I have remarked has been in the number of successive 
shocks acting through the turpentine. The shocks are generally fewer than when 
there is no turpentine. Thus with a very small jar, and without the turpentine, five 
or six, and even as many as ten successive shocks may be obtained, and which cause 
the contraction; and when the turpentine has been interposed, the shocks are from 
four to six. The depth of the insulating stratum was always such that a current from 
a pile of fifteen couples of plates could not penetrate it. 
I have gilded the muscular conductor, and stretched the galvanoscopic nerve upon 
its surface ; on passing shocks from the small jar I still had contractions in the gal- 
vanoscopic frog. In this case also it is to be observed that contraction never went 
bevond the second or third discharge. 
» o 
Finally, on interposing very fine plates of mica between the surface of the muscle 
and the galvanoscopic nerve, the frog contracted at two or three successive discharges 
from the small jar. I will here call attention to a fact somewhat remarkable, which has 
always occurred in these experiments: on passing the first shock of the jar accom- 
panied by the spark, the contraction of the galvanoscopic frog almost invariably fails. 
