Dr. Gerald Yeo, late Professor of Physiology at King's College, read a very interesting paper before the College Society in 1883 ('The Nervous Mechanism of Hypnotism'), in which he propounded some interesting theories on the subject of hypnotic phenomena, and illustrated them by experiments on animals. He showed how animals of such diverse organization as crayfish, frogs, fowls, and guinea-pigs could be easily hypnotized by monotonous continuous stimulation, and made to remain motionless and unresponsive to ordinary stimulation. He induced this state by firmly fixing them in one position for a few minutes, and then gently removing the restraining influence, when it was found the animals continued in that position, however abnormal, for several minutes. Kircher's experiment with the domestic fowl is the most familiar example of hypnotic effect in animals. If a chalk line is drawn and the bird held for a few seconds with its beak on this line, it will be found that the creature remains in that position for several minutes. Dr. Yeo, however, says that the line is unnecessary in performing this experiment.

Dr. Ralph Vincent (op. cit.) relates various experiments he has made on hypnotized cats, rabbits, toads, and other animals.

The plan of changing the nest of a sitting hen, familiar to farmers, probably depends on hypnotism for its success. The fowl's head is firmly held under its wing for a few minutes, and she is carried from one nest to another. She seems ignorant of the change, and continues sitting on the new set of eggs until they are hatched, or she is again removed to another nest in the same way. The drowsy condition induced in many animals by gentle friction of the forehead is a matter of common observation; and I have frequently seen negroes in South America reduced to a condition of drowsiness verging on somnambulism by the gentle stroking of the head and manipulation of the hair which they seem to be so fond of at the hands of their womankind.