There he stayed for about five years, expounding his views on the pathology of the nervous system in numerous lectures which attracted considerable attention.

He relinquished this position in 1867, and in 1869 became professor at the École de Médecine in Paris, but in 1873 he again returned to America and began to practice in New York City.

[5][6][7] Brown-Séquard was quite a controversial and eccentric figure, and is also known for claiming, at age 72, rejuvenated sexual prowess after subcutaneous injection of extracts of animal testis.

[10] The positive response by many men is now thought to have been a placebo effect, but apparently this was "sufficient to set the field of endocrinology off and running.

At age 72, at a meeting of the Societé de Biologie in Paris, Brown-Séquard reported that hypodermic injection of a fluid prepared from the testicles of guinea pigs and dogs leads to rejuvenation and prolonged human life.

A Vienna medical publication quipped dismissively: "The lecture must be seen as further proof of the necessity of retiring professors who have attained their threescore and ten years.

"[12] Brown-Séquard's research, published in about 500 essays and papers, especially in the Archives de Physiologie, which he helped to found in 1868 along with Jean-Martin Charcot and Alfred Vulpian, cover a very wide range of physiological and pathological subjects.