Here's the scoop on nutmeg, thanks to Wikipedia (bold type is mine):
In low doses, nutmeg produces no noticeable physiological or neurological response, but in large doses, raw nutmeg has psychoactive effects. In its freshly ground form (from whole nutmegs), nutmeg contains myristicin, a monoamine oxidase inhibitor and psychoactive substance. Myristicin poisoning can induce convulsions, palpitations, nausea, eventual dehydration, and generalized body pain. It is also reputed to be a strong deliriant. For these reasons, nutmeg has been banned in Saudi Arabia.
Intoxications with nutmeg had effects that varied from person to person, but were often reported to be an excited and confused state with headaches, nausea, dizziness, dry mouth, bloodshot eyes, and memory disturbances. Nutmeg was also reported to induce hallucinogenic effects, such as visual distortions and paranoid ideation. Intoxication took several hours before the maximum effect was reached. Effects and aftereffects lasted up to several days.
Myristicin poisoning is potentially deadly to some pets and livestock, and may be caused by culinary quantities of nutmeg harmless to humans. For this reason it is recommended not to feed eggnog to dogs.
Swiss chemist Albert Hofmann, who discovered LSD, and Harvard ethnobotanist Richard Evans Schultes documented reports of nutmeg's use as an intoxicant by students, prisoners, sailors, alcoholics, and marijuana smokers. In his autobiography, Malcolm X writes about taking nutmeg and other "semi-drugs" while serving time in prison.
The Angewandte Chemie International Edition records the use of nutmeg as an intoxicant in the United States in the post-World War II period, notably among young people, bohemians, and prisoners. A 1966 New York Times piece named it along with morning glory seeds, diet aids, cleaning fluids, cough medicine, and other substances as "alternative highs" on college campuses.