There is a very striking distinction between the permanent stimulants; one section confining their direct influence to the vital function of organic contractility, the other operating upon the vital functions generally. The first division is very appropriately denominated astringents, the second less appropriately tonics. They constitute two of the ultimate classes of remedies.

1. Astringents are medicines which produce contraction of the living tissues.

2. Tonics are characterized by their general stimulating influence over the functions, operating slowly, moderately, and somewhat durably, either directly through the circulation, or secondarily through the digestive function.