494 PROFESSOR MATT EUC Cl’S ELECTRO-PHYSIOLOGICAL RESEARCHES. 
ments, is the longer or shorter repose given to the nerve which has previously been 
acted upon for a considerable time by the inverse current. In one of these experi- 
ments the contraction was 14° on opening the inverse circuit which had been long 
closed. Leaving the circuit incomplete for five seconds, and then completing it and 
breaking it again immediately afterwards, the contraction was only 4°. Again, I 
complete the circuit, and on breaking it, after the inverse current has been passed 
for ten seconds, the contraction again amounts to 14°. In another experiment it 
was also 14° on opening the inverse circuit, which had remained closed during 120 
seconds. Opening the circuit, and after two seconds closing, then breaking it im- 
mediately afterwards, the contraction did not exceed 10°. Then closing again, and 
allowing the current to pass for sixty seconds, the contraction again became 14°, as 
in the beginning. Breaking the circuit again, and leaving the nerve in quiet for 
sixty seconds, I complete the circuit and open it again immediately, and the contrac- 
tion does not exceed 8°. In another experiment, on opening the circuit after the 
nerve had been acted upon by the inverse current for sixty seconds, the contraction 
amounted to 18°. I then left the nerve in repose for five seconds, after which, closing 
the circuit and breaking it again immediately, the contraction was 12°. After twenty- 
five seconds of repose the contraction was 8° : finally, leaving the inverse circuit closed 
for five seconds, the contraction, on breaking the circuit, was again 18°, as at the 
commencement. It is therefore also proved by these as well as by all the former ex- 
periments, that the increased excitability produced by the passage of the inverse current 
persists after the current has ceased for a time varying in length, according to the pri- 
mitive excitability of the nerve ; if the excitability of the nerve is very great, the 
increase produced by the passage of the inverse current ceases immediately, or almost 
immediately, after breaking the circuit; while it persists longer if the excitability of 
the nerve is already weakened. 
Up to this point we have only studied the action of the inverse current upon the 
mixed nerves of the prepared frog, so that the increase of excitability produced by the 
passage of the inverse current must necessarily be in some measure hindered by the 
weakening of this excitability, the consequence of death. It was therefore necessary 
to study the action of the inverse current upon a living animal. At page 200, and 
in the following pages of my Treatise on the Electro-Physiological Phenomena of 
Animals, I have described some experiments of this kind, which I have subsequently 
repeated. When a current from a pile, direct or inverse, is passed along the sciatic 
nerve of a live rabbit, it always occasions violent contractions of the lower limbs and 
of the entire trunk ; the animal screeches and agitates itself. These phenomena pre- 
sent themselves equally with the direct and with the inverse current, both at the 
commencement and at the end ; but a difference very soon appears if the circuit re- 
mains closed. With the direct current the contraction is soon over, and the leg 
alone contracts when the circuit is closed. With the inverse current the symptoms 
of pain remain when the circuit is closed, as also the contraction in the leg when the 
