More conclusive still is the fact that animals can be hypnotized. Albert Moll, who is one of the ablest, and certainly one of the most unprejudiced, of modern scientific writers on the subject of hypnotism, writing from the standpoint of the Nancy school, makes the following observations on the subject of hypnotizing animals:-- "States resembling, or perhaps identical with, hypnosis, are also found in animals, and can easily be experimentally induced. The first experiments of this kind are referred to by the Jesuit Kircher,--the so-called _experimentum mirabile Kircheri_. Kircher described these experiments in 1646; but according to Preyer, the experiment had been made by Schwenter several years earlier. The most striking of these experiments, which are being continued in the present day, is as follows: 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 ascribes this to the animal's imagination; he said that it imagined that it was fastened, and consequently did not try to move. 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 made a series of experiments like Czermak's. Preyer, however, distinguishes two states in animals,--catalepsy, which is the effect of fear; and the hypnotic state. Heubel, Richet, Danilewsky, and Rieger, 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. I 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, or catalepsy, produced by a sudden peripheral stimulus. In any case they vividly recall the catalepsy of the Salpêtrière, also caused by a strong external stimulus."[18]