Psychology (Briefer Course)

Thus, if the breast be touched, both fore-paws will rub it vigorously; if we touch the outer side of the elbow, the hind-foot of the same side will rise directly to the spot and wipe it. The back of the foot will rub the knee if that be attacked, whilst if the foot be cut away, the stump will make ineffectual movements, and then, in many frogs, a pause will come, as if for deliberation, succeeded by a rapid passage of the opposite unmutilated foot to the acidulated spot. Fig. 39. — C, H, cerebral hemispheres; O Th, optic thalami; O L, optic lobes; Cb, cerebellum; M O, medulla oblongata; S C, spinal cord. The most striking character of all these movements, after their teleological appropriateness, is their precision. They vary, in sensitive frogs and with a proper amount of irritation, so little as almost to resemble in their machine- like regularity the performances of a jumping-jack, whose legs must twitch whenever you pull the string.