In order to impress the memory and facilitate investigation, it is necessary that medicinal substances should be classified according to their similarity of action on the animal economy, as follows:

1. Neurotics, or those which have a special action on and modify the functions of the nervous system. To this group belong:

Hypnotics and

Narcotics,

Anaesthetics,

Antispasmodics,

Tonics,

Astringents,

Stimulants,

Sedatives,

Spinants.

2. Eccritics, or those which have a special action on the secretions. To this group belong:

Emetics,

Cathartics,

Diaphoretics,

Diuretics,

Blennorrhetics,

Emmenagogues.

3. Hemetics, or those which modify the blood. To this group belong:

Hematinic Alterative Antacids.

4. Topical Remedies. To this group belong:

Irritants,

Demulcents,

Antiseptics,

Disinfectants,

Coloring Agents,

Anthelmintics.