The many transitional states between waking life and hypnosis will often make the question difficult to decide; none of the points above mentioned will alone suffice to settle it. The cases of fascination and analogous states of normal life mentioned on pages 73 and 74, show that there is no very sharp line of distinction between hypnosis and waking life. From this we can see, on the one hand, the resemblance of many of the phenomena of hypnosis to those of waking life, and, on the other, how difficult it is to decide exactly where hypnosis begins.

States resembling, or perhaps identical with hypnosis, are also found in animals, and can easily be experimentally induced. The first experiment of this kind is usually attributed to the Jesuit father Kircher; - the so-called experimentum mira-bile Kircheri. Kircher described this experiment in 1646; but according to Preyer, it had been made by Schwenter several years earlier. A hen is held down on the ground; the head in particular is pressed down. A chalk-line is then drawn on the ground, starting from the bird's beak. The hen will remain motionless. Kircher ascribed this to the animal's imagination; he said it imagined it was fastened, and consequently did not try to move. Mach mentions Kircher's experiment in his book, Erkentniss und Irrlum, as a proof of the ease with which an experiment may be erroneously interpreted. For a long time the chalk-line was held to be the essential part of the experiment, producing some far-reaching mental action on the part of the hen; later on, however, it was shown that the experiment could be successfully performed by merely holding the hen down on the ground, and the chalk-line was consequently but of secondary importance.

Czermak repeated the experiment on different animals, and announced, in 1872, that a hypnotic state could be induced in other animals besides the hen. Preyer shortly after began to interest himself in the question, and distinguished two states in animals - cataplexy, which is the state of fear, and the hypnotic state. Regnard observed that when dynamite explosions took place in the water, fish that were not in the immediate neighbourhood of the charge would lie as if dead, though a slight touch would restore movement. Laborde found the same true of trout, which could thus be caught. Heubel, Richet, Danilewsky, Rieger, Gley, Verworn, and Micheline Stefanowska, besides the authors mentioned above, have occupied themselves with the question.

Most of the experiments have been made with frogs, crayfish, guinea-pigs, and birds, and by Verworn with the hooded snake. I myself have made many with frogs. This much is certain: many animals will remain motionless in any position in which they have been held by force for a time. There are various opinions as to the meaning of this. Preyer thinks many of these states are paralyses from fright (cataplexy), produced by a sudden peripheral stimulus. In any case, they recall the catalepsy of the Salpetriere, also caused by a strong external stimulus. It is said a sudden Drummond limelight produces the same effect on a cock that it does on hysterical patients (Richer). But in general, the external stimulus used with animals is tactile, as in suddenly seizing them. Heubel thinks that these states in animals are a true sleep following on the cessation of the external stimuli, and Wundt seems to agree with him. Rieger has shown that the frog will remain rigid when upright, if kept from falling, as well as when lyirig on its back. The hind leg of a frog lying on its back may be pulled out, and the animal will not draw it in again as it usually does. Richer,, however, says that it is drawn in again at once if the spinal cord is divided below the medulla oblongata.

It is interesting that when a "hypnotic" frog is placed in a certain position it will at first move after a short time, but the more often the experiment is repeated the longer the frog lies without moving. I have seen frogs lie on their backs in this way for hours, and have even often seen them die without turning over. The deeper the state is, the less the animal responds to external stimuli; it ends by not moving to tolerably loud noises, or even stimulation of the skin. Danilewsky made a series of experiments, from which he concluded that there were regular changes of reflex excitability; but Rieger was unable to confirm this. According to Danilewsky, when the cerebral hemispheres are removed the frog assumes cataleptoid postures, and further that the rotatory movements caused by injury to the semi-circular canals of the ear disappear in hypnosis. Harting's experiments also deserve mention; after repeated hypnotic experiments with fowls he observed hemiplegic phenomena in them, according to a communication by Milne-Edwards to the Paris Academy of Sciences. I may here recall the fact that Lodder once reported a case in which he considered that hypnotic phenomena were associated with an attack of cerebral hemiplegia.

In 1898, Verworn propounded a physiological theory of his own in a work in which he dealt with the "so-called hypnosis of animals." He has formed the opinion that the states observed in animals have nothing to do with hypnosis in man; at the same time he certainly considers suggestion of chief import in the case of human beings. In his opinion, we must base our conclusions upon the attitude of the animal and the condition of its muscular system, which alone are decisive. For any particular position in which an animal may be placed, it assumes a characteristic attitude corresponding to the reflex which tends to restore it to a normal posture. The muscles which participate in this reflx action remain in a state of tonic contraction. The same characteristic complexus of symptoms occurs when the animal's cerebrum has been removed, and from this very fact Verworn concludes that there can be no question of suggestion. But the phenomenon is made up of two components. The chief of these, and that which causes the characteristic symptoms, is the tonic state of excitation in that cerebral sphere which controls the reflex in question; a subordinate component is the inactivity of the motor spheres of the cerebral cortex, as shown by the absence of spontaneous efforts to rise.