From 1978 until 2000 Forel’s image appeared on the 1000 Swiss franc banknote.
Although professionally Forel was one of the important psychiatrists of the last century, he is primarily known as an ant specialist. When very young he went on a study trip to southern Switzerland; the published results of his observations at once brought him high repute as an entomologist and earned him the Schläfli Foundation Prize. As an anatomist Forel studied the internal morphology of ants carefully and thus came to propose a new taxonomy of these members of the order Hymenoptera. In addition, having become engrossed in the psychology of these insects, he contributed greatly to the study of their social instincts. Forel was the first to describe the phenomena of parabiosis (the natural or artificial joining or grafting of two organisms) and lestobiosis (the relation in which colonies of a small species nest in the walls of the nest of a larger species and enter the chambers of the larger species to prey on brood or rob the food stores) in ants. Having gathered a considerable collection of Hymenoptera he described the various species, finding more than 3.500 new ones. Thus he became a remarkable taxonomist.
Research on hypnotism also fascinated him, he wrote many papers on that subject and was considered and authority on the treatment of mental disturbances with hypnosis. Hygienist as well, Forel published the important book La question sexuelle, which was translated into nearly twenty languages.
Forel enumerates the following conditions and diseases which he finds most satisfactorily treated by hypnotic suggestion[PSYCHO-THERAPEUTICS - TREATMENT BY HYPNOTISM AND SUGGESTION-1907]:
Pains of all descriptions, especially headache, neuralgia, sciatica, toothache, which do not depend upon an abscess, etc.
Functional paralysis and contractures.
Organic paralysis and contractures (as palliative means).
Chlorosis (extremely favourable).
Disturbances of menstruation (metrorrhagia and amenorrhoea).
Loss of appetite and all nervous digestive disturbances.
Constipation and diarrhoea (provided that the latter does not depend on catarrh or fermentation).
Gastric and intestinal dyspepsia (including pseudo-dilatation).
Psychical impotence, pollutions, onanism, perverted sexual appetite, and the like.
Alcoholism and morphinism (only by the suggestion of total abstinence).
Chronic muscular and arthritic rheumatism, lumbago.
The so-called neurasthenic disturbances.
Stammering, nervous disturbances of the vision.
Pavor nocturnus of children.
Sickness and sea-sickness, the vomiting of pregnancy.
Enuresis nocturna (often very difficult on account of the depth of the normal sleep).
Nervous attacks of coughing (also in emphysema).
Hysterical disturbances of all kinds, including hystero-epileptic attacks, anesthesia, phobia, and the like.
Bad habits of all kinds.