Using the word "somnambulists" to refer to those hypnotized, an 1831 report by a committee of French medical authorities, under the auspices of the Royal Academy of Medicine, stated the following:
"The greater number of the somnambulists whom we have seen, were completely insensible. We might tickle their feet, their nostrils, and the angle of the eyes, with a feather—we might pinch their skin, so as to leave a mark, prick them with pins under the nails, &c. without producing any pain, without even their perceiving it. Finally, we saw one who was insensible to one of the most painful operations in surgery, and who did not manifest the slightest emotion in her countenance, her pulse, or her respiration."
The author of one work tells us of his personal observations on this topic, using "mesmeric" to mean "hypnotic":
"In the first experiment I ever tried to assure myself of the reality of mesmeric anathsesia, a young woman was put to sleep and eight bad teeth were extracted from her ulcerated gums without her having any consciousness of it. But her inner consciousness being at the same time aroused, she was able to tell me the time by a clock in a house eight miles away, as I verified the next day by comparison with my watch."
The report above combines two inexplicable aspects of a hypnotic trance, an insensitivity to pain, and also clairvoyance during a hypnotized state, which is abundantly attested to in other reports discussed here and here and here.
On pages 27-28 of a book by Dr. James Esdaile he lists a host of dramatic painless surgeries he performed without using anesthesia, but only hypnosis on patients. The list includes about 20 amputations, and 200 removals of scrotal tumors ranging from 10 pounds in weight to more than 100 pounds in weight. Another book on this topic by Esdaile can be read here.
In the following quote from a nineteenth century work, we learn of a great irony: that physicians took up a chemical method of anesthesia, one which would often kill people, rather than using hypnotic methods of anesthesia that were proving very safe and effective:
"In Dr. Brown Sequard's lectures upon 'Nervous Force,' delivered in Boston in 1874, he speaks of this form of anaesthesia as follows :
'As regards the power of producing anaesthesia, it seems to me unfortunate that the discovery of ether was made just when it was. It was, as you well know, in 1846 or 1847 that the use of ether as an anaesthetic was begun. It started from this city (Boston). At that time in England, Dr. Forbes was trying to show from facts observed in England, and especially in India, from the practice of Dr. Esdaile, that something which was called Mesmerism, but which, after all, was nothing but a peculiar state of somnambulism induced in patients, gave to them the idea that they were deprived of feeling ; so that they were in reality under the influence of their imagination, and operations were performed that were quite painless. I say that it was a pity that ether was introduced just then, as it prevented the progress of our knowledge as to this method of producing anaesthesia. My friend Dr. Broca took it up in 1857-8 and pushed it very far; and for a time it was the fashion in Paris to have amputations performed after having been anaesthetized by the influence of Braidism or Hypnotism. A great many operations were performed in that way that were quite painless. But it was a process that was long and tedious, and surgeons were in a hurry and gave it up. I regret it very much, as there has never been a case of death from that method of producing anesthesia, while you well know that a great many cases of death have been produced by other methods.' "
A modern paper reports a similar result: hypnosis producing dramatic reduction in headache pains. We read this:
"Symptoms of headache and vertigo were treated using direct hypnotic suggestions of symptom relief in 155 consecutive skull injured patients. Posttraumatic headache and vertigo were completely relieved after an average observation period of 1 year 10 months in 50% and 58% of the patients, and partially relieved in 20% and 16% respectively."
The difference here is that this pain reduction comes after the patient leaves the hypnotized state.
"Sensitiveness is entirely abolished. The patient hears only the voice of the magnetizer and that of the person whom the latter places en rapport with him. His deafness is absolute for all noises that occur, of whatsoever intensity. In an experiment made at Paris, a sceptic fired a pistol near the ear of a somnambule. The latter heard nothing. The insensibility is not less complete in other parts of the body. We may bury needles in the flesh without the patient feeling the least pain. He suffers only when he awakes. The most painful surgical operations have been performed on magnetized subjects, and they had only learned what had happened after they had come out of their sleep."
Phenomenon #4: clairvoyance and ESP during a hypnotic trance.