Insensibility to impressions from without is another phenomenon which magnetic sleep has in common with many other conditions. It is produced by anæsthetics like chloroform and ether, by utter exhaustion in consequence of long suffering, as was the case with martyrs and prisoners subjected to torture, and by excessive loss of blood. But in magnetic sleep it reaches a higher degree than under other circumstances; cataleptic patients, and even clairvoyants in moments of greatest excitement, seem to be in a state in which the nerves cease to act as conveyers of impressions to the brain. This has often led to unwarrantable abuse; physicians, under the pretext of scientific investigation, inflicting severe injuries upon their patients, utterly unmindful of the fact that, however great the momentary insensibility may be, the sense of pain returns at the instant of re-awaking. On the other hand, physicians have taken advantage of this state of unconsciousness of pain, in order to perform serious operations. The first instance of a surgical operation being attempted while the patient was in mesmeric sleep, was that of Madame Plantin, a lady of sixty-four years, who suffered of cancer in the breast. A Mr. Chapelain prepared her by throwing her for several days into a trance by means of the usual mesmeric passes. She then manifested the ordinary symptoms of somnambulism, and conversed about the impending danger with perfect calmness, while she contemplated it, when conscious, with the utmost horror and apprehension. On the 12th of April, 1824, she was again thrown into a trance, and the painful and dangerous operation accomplished in less than a quarter of an hour, while she conversed with the surgeon, the famous Dr. Ploquet, and showed in her voice, her breathing, and her pulse not the slightest sign of excitement or pain. When the wound was bound up, she awoke, but upon hearing what had taken place, she became so violently excited that the magnetizer had to cause her once more to fall asleep under his passes. And yet, in spite of this brilliant success, when Dr. Warren of Boston asked the great surgeon why he had never repeated the experiment, the latter was forced to acknowledge that he had not dared do it, "because the prejudice against mesmerism was so strong in Paris that a repetition would have imperiled his position and his reputation!" Since that time mesmerism has been repeatedly, and almost always successfully employed as an anæsthetic; Dr. James Esdall, chief surgeon of the presidency of Calcutta, having reduced the application to a regular method. Dr. Forbes reports two cases of amputation of the thigh in magnetic sleep, which were successful, and similar experiments have been made in England, and in India, with the same happy result.