Yet even here we can by no means feel certain. Physicians have invented various ingenious pieces of apparatus for testing the circulation and other physiological conditions; but even these things are not sure tests. The writer knows of the case of a man who has such control over his heart and lungs that he can actually throw himself into a profound sleep in which the breathing is so absolutely stopped for an hour that a mirror is not moistened in the least by the breath, nor can the pulses be felt. To all intents and purposes the man appears to be dead; but in due time he comes to life again, apparently no whit the worse for his experiment. If an ordinary person were asked to hold out his arms at full length for five minutes he would soon become exhausted, his breathing would quicken, his pulse-rate increase. It might be supposed that if these conditions did not follow the subject was in a hypnotic trance; but it is well known that persons may easily train themselves to hold out the arms for any length of time without increasing the respiration by one breath or raising the pulse rate at all. We all remember Montaigne’s famous illustration in which he said that if a woman began by carrying a calf about every day she would still be able to carry it when it became an ox. In the Paris hospitals, where the greater number of regular scientific experiments have been conducted, it is found that “trained subjects” are required for all of the more difficult demonstrations. That some of these famous scientists have been deceived, there is no doubt. They know it themselves. A case which will serve as an illustration is that of Dr. Luys, some of whose operations were “exposed” by Dr. Ernest Hart, an English student of hypnotism of a skeptical turn of mind. One of Dr. Luys’s pupils in a book he has published makes the following statement, which helps to explain the circumstances which we will give a little later. Says he: