"In surgical operations performed while the patient lay under the influence of an anæsthetic, as chloroform or ether, I have witnessed contortions of the whole muscular system, and heard outcries so fearful that it was impossible to persuade the lookers-on that the application of the instrument was not causing the severest agony. Upon one occasion I myself stood by a man who was to suffer a difficult dental operation, and with my own hands administered chloroform to him. All the usual symptoms of complete anæsthesia ensuing, I signaled the dentist to begin his work. The moment that the instrument came into successful operation, the patient uttered a harrowing cry of pain and struggled convulsively, at the same time entreating the operator to stop. I was persuaded, from former cases of a similar nature, that the man had no consciousness of pain, and so advised the dentist. From motives of humanity, however, the latter desisted when his work was but partly accomplished, and, having extracted a single tooth instead of the several which were to be drawn, permitted the seeming sufferer to return to his natural state. He presently awoke, as from a dream; and on being asked whether he endured great torture, he laughed at the idea, denying that he had even been aware of the application of the forceps, although fully self-conscious internally during the whole effect of the anæsthetic.SOURCE: Ludlow, Fitz Hugh "The Mysteries of the Life-sign Gemini" The Hasheesh Eater
I believe I am only stating one of many cases which fall under the almost daily observation of men of wide experience in the surgical profession. Although far from being an expert myself, I have been an eye-witness to two such instances."