uralist, Herr Geupel-White, has most kindly placed at our disposal the rich material his zoological garden affords, to assist us in these experiments.
My former experiment with the swan was also performed in Herr Geupel-White's garden. In the experiments with the small birds, the condition of immobility, which can change to actual sleep, is only caused by the effect of the impression made in the animals, through touching the skin and overpowering the resisting muscles. You will see this in the continuation of our experiment. That, however, the exciting of certain cutaneous nerves alone changes the normal functional capacities, and calls forth a singular state of stupidity, is proved by the following highly-interesting experiment with a frog, which Dr. Lewissohn, in Berlin, has suggested, and most thoroughly investigated:
If one places a frog on its back, it does not remain in this unnatural position for an instant, but, on the contrary, turns itself over and escapes. This you may see yourselves, when I endeavor to place this frog on its back. But please notice the astonishing result if we tie its two fore-legs with a string. (The lecturer tied threads around each of the frog's fore-legs, drew the threads tightly, and laid the animal, as before, on its back.) You see that the frog, breathing heavily but otherwise quite motionless, now lies on its back, and does not make the slightest attempt to escape, even when I endeavor to move it. It is as though its small amount of reasoning power had been charmed away, or else that it slept with open eyes; an analogous condition to that which we saw in the crabs, hens, and little birds. The only difference is, that the actual connection of the phenomena is much clearer. Now, I press upon the cutaneous nerves of the frog, while I loosen and remove the threads on the fore-legs. Still the animal remains motionless upon its back, in consequence of some remaining after-effect; at last, however, it returns to itself, turns over, and quickly escapes.
That it is here a matter of restraint upon the nervous centres, in consequence of the pressure on the sensitive cutaneous nerves, Lewissohn has already proved. In this experiment, the impulse of motion on the nervous fibres, which proceeds from the so-called motory centre of the brain and spinal cord, remains quite capable of action on one side, while, as regards the other side, the remarkable condition of stupidity will no longer happen, if we have divided the cutaneous nerves before tightening the threads.
Sometimes it is possible to make the frog lie motionless on its back without the threads; but this proves nothing against the soundness of Dr. Lewissohn's results.
But let us return to our old experimentum mirabile[1] of the hen. According to the analogy of the last experiments with the frog, the tying together of the hen's feet, although not necessary, may contribute something to the effect in Kircher's experiment, not only by
- ↑ Admirable experiment.
