These may be classified as follows: Class I. - Acting on the cerebrum.

A. Cerebral depressants or soporifics:

Opium, Hops, Lactucarium, Pellotine.

B. Cerebral excitants:

Deliriants

Belladonna.

Strarndriium.

Hyoscyamus.

Also act on nerve endings in glands and involuntary muscle.

Duboisine. Cannabis Indica. Caffeine, Guarana.

Class II. - Acting on the spinal cord.

A. Exciting the cells of the anterior cornua. Nux Vomica,

Strychnine.

B. Depressing the cells of the anterior cornua. Calabar bean,

Muscarine, Gelsemium.

Class III. - Acting on the nerves.

A. Depressing the motor nerves. Conium, Tobacco.

B. Depressing the motor end plates. Curare. C. Depressing the sensory nerves. Coca, Cocaine.

D. Stimulating the secretory nerves. Pilocarpus.