PROFESSOR MATTEUCCI’S ELECTRO-PHYSIOLOGICAL RESEARCHES. 
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tractions which are obtained are very feeble, particularly if the weight attached to 
the limb, to bring it back to its position after the contractions have ceased, be ex- 
tremely small. If we continue to operate on this same frog, we see the contractions 
become stronger and increase during a certain time. In all cases the muscles of 
frogs killed and prepared rapidly, are stiff, and seized with a kind of tetanic contrac- 
tion ; while the muscles are in this state, the contractions which are obtained by 
the passage of the electrie current are necessarily less strong than those which are 
developed when these same muscles have ceased to be contracted naturally. 
After having repeated some experiments of this kind with the dynamometer, I soon 
came to the conviction that this was the real eause of the phenomenon under obser- 
vation. I shall only give one of these experiments, which proves the truth of this 
explanation. 
I operated on very vigorous frogs, four of whieh had had the spinal marrow di- 
vided twenty-four hours before experiment, and four other similar frogs which were 
intaet. 
The following are the numbers found immediately after the preparation : — 
Contraction of the frog of which the spinal marrow Contraction of the frog in the 
had been divided for 24 hours. natural state. 
30 
28 
26 
24 
26 
24 
24 
20 
I left the frogs untouehed for forty minutes, and then repeated the experiment: 
the following are the results : — 
10 
8 
8 
8 
22 
20 
16 
16 
The difference of contraction obtained in the two experiments is therefore evidently 
due to the state of the muscles differing in the two cases, according to whether the 
frog was submitted to experiment immediately after death, or whether it had had the 
spinal marrow divided for a long time, and consequently the muscle relaxed for a 
considerable period. The contractions excited by the electric current in a frog im- 
mediately after death, are feeble at first, on aeeount of the nearly tetanic condition of 
the muscles ; whereas, if left in repose, so as to give time for the muscles to become 
relaxed, the contractions then excited by the current are stronger. The contrary to 
this occurs if the experiment be made on a frog the muscles of which have been 
for some time without contraction, in consequence of the spinal marrow having been 
