. . . I gently pinch the toes. . . . The
leg of the same side is pulled up. . . . I pinch the same more severely.
. . . Both legs are thrown into motion.
Having thus satisfactorily proved that the wretched creature could still
suffer acutely, the professor resumed:
The cutaneous nerves of the frog are extremely sensitive to acids; so
I put a drop of acetic acid on the outside of one knee. This, you see,
gives rise to most violent movements both of arms and legs, and notice
particularly that the animal is using the toes of the leg on the same
side for the purpose of rubbing the irritated spot. I dip the whole
animal into water in order to wash away the acid, and now it is all
at rest again. . . . I put a drop of acid on the skin over the lumbar
region of the spine. . . . Both feet are instantly raised to the
irritated spot. The animal is able to localize the seat of irritation.
. . . I wash the acid from the back, and I amputate one of the feet at
the ankle. . . . I apply a drop of acid over the knee of the footless
leg.
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