Elliotson was a prolific and influential author, a respected teacher, and renowned for his diagnostic skills as a clinician and, especially, his extremely strong prescriptions: "his students said that one should let him diagnose but not treat the patient".

(1841), the University College's Professor of Clinical Surgery, one of the fastest surgeons of all time (on one occasion Liston amputated a leg, mid-thigh, in 25 seconds), who was pale skinned, and at least 6 ft 2in (188 cm) tall.

[21] Elliotson and William Collins Engledue were the co-editors of The Zoist: A Journal of Cerebral Physiology & Mesmerism, and Their Applications to Human Welfare, an influential British journal, devoted to the promotion of the theories and practices (and the collection and dissemination of reports of the applications) of mesmerism and phrenology, and the enterprise of "connecting and harmonizing practical science with little understood laws governing the mental structure of man",[22] that was published quarterly, without a break, for fifteen years: from March 1843 until January 1856.

[23] In 1846 – by this stage bereft of all his institutional affiliations – and despite many earnest efforts made to prevent him doing so, as the Royal College of Physicians' youngest fellow, Elliotson delivered the Harveian Oration to the Royal College of Physicians of London,[24] in which he controversially spoke of how William Harvey, the man whom the Oration was honouring, had been forced to fight against the entrenched conservatism of the medical profession and its initial incredulity and resistance to his discoveries, and stressed the strength of the analogy with the current (equally misguided and ignorant) critics of mesmerism.

For example, the Lancet called him a professional pariah, stated that his oration would strike a vital blow at legitimate medicine, and would be a black infamy degrading the arms of the College.

Without referring to the attacks which had been made upon him, he simply stated the result of his researches, and respectfully invited the College to examine alleged facts of overwhelming interest and importance.

He exhorted his hearers to study mesmerism calmly and dispassionately, and reminded them, with more truth than tact, that all the greatest discoveries in medical science, and the most important improvements in its practice, had been opposed by the profession in the most violent and unprincipled manner.

As examples of scientific discoveries which had been received in this way, he cited those of the lacteal vessels, the thoracic duct, the sexual system of plants, the circulation of the blood, the sounds of the chest and their relation to the diseases of the heart and lungs and their coverings, etc.

As instances of improvement in practice which had been treated in like manner, he referred to the employment of Peruvian bark, inoculation and vaccination for small-pox, the use of mild dressings, instead of boiling oil, in gun-shot wounds, the ligature of the bleeding vessels after operation, instead of the application of burning pitch or red-hot irons, etc.

In his opinion many of these were indisputable; for ten years he had shown how mesmerism could prevent pain during surgical operation, produce sleep and ease in sickness, and even cure many diseases which had been unrelieved by ordinary methods.

— John Milne Bramwell (1903)[25]Elliotson continued to provide mesmeric demonstrations from his own residence at 37 Conduit Street, Hanover Square (which he eventually quit in 1865).

As his reputation rapidly declined, his once lucrative practice also disappeared, and he died, penniless, in 1868 in the London home of a medical colleague, Edmond Sheppard Symes (1805-1881), L.S.A.

Elliotson's approach to the mind was through the body … In addition, Elliotson was the first to attempt to detach the operations of mesmerism and the conditions of the procedure from conscious acts of will on the part of the subject and the operator, the patient and the doctor … In his appreciation of the non-rational and non-conscious elements within the procedure, [he] gave some direction and encouragement to those forces … that were laying the groundwork for Freud and other exponents of the relationship between the unconscious and psychiatric therapy.

[30] Elliotson is a major antagonist in the game Assassin's Creed: Syndicate, who performs brutal and fatal experiments on the insane at Lambeth Asylum and is a secret member of the Templar Order.