From his experimental work Horsley produced evidence to support the view that myxoedema, cretinism and operative cachexia strumpriva are all due to thyroid deficiency.

By experimental removal of the thyroid Horsley produced artificial myxedema, confirming previous work by Reverdin and others. At the time his results were regarded as proof that total thyroidectomy produces operative myxedema, but some of the symptoms he described are now known to have been due to removal of the parathyroids.

First successful experimental hypophysectomy; two dogs survived five and six months respectively after this operation.

Beevor, physician to the National Hospital, Queen Square, London, collaborated with Horsley in an important series of investigations of the localization of cerebral function.

Horsley was the founder of neurosurgery in England. The above paper records the first successful operation for the removal of an extramedullary tumor of the spinal cord.

A detailed analysis, by means of faradic stimulation, of the motor responses of the cerebral cortex, internal capsule, and spinal cord of higher primates.

Gotch and Horsley showed that electric currents are produced in the mammalian brain, and they recorded them with the string galvanometer of the capillary electrometer. Their work led eventually to the development of the electroencephalograph.

Horsley, with J. Taylor and W. S. Coleman, devised an operation for treatment of trigeminal neuralgia in which the Gasserian ganglion was removed by a temporal approach.

Stereotactic apparatus for the accurate location of electrodes in the brain. The apparatus devised by Horsley and Clarke opened the way to stereotactic surgery of the brain.

Horsley demonstrated that removal of the precentral area in man abolished athetosis.