Morphine is the most important alkaloid of opium, and is generally used as the sulphate.

It has no action on the skin or mucous membranes, but is quickly absorbed from the latter.

In animals it stimulates the spinal cord, but in man it quiets and stupefies the brain, finally producing coma. It slightly dulls the sensibility of the sensory nerves, but stops sensation mostly by action on the cerebral nerve centers. It slows the respiration by acting on the respiratory center, dries up secretions, and stops peristalsis. It produces death by paralyzing the respiratory center.

It is excreted into the stomach and in the urine.