A member of the Passaflorinece. It resembles the Cncurbitaceae in the form of its fruit, and by some authorities it is placed in a separate class—the Papayaceae.

Composition

The young fruit when incised furnishes an abundance of milky fluid, which is slightly bitter to the taste, and it coagulates on exposure to the air, separating into an albuminous clot and a transparent liquid resembling in this process the coagulation of blood.

The juice contains a digestive ferment which is called papain, sometimes papayotin. It is an albuminous substance, white, amorphous, soluble in water, but insoluble in alcohol and ether. The dose of papain ranges from 5 to 30 grains.

From the leaves of the plant an alkaloid has been obtained, called by its discoverer, Yon Greshoff, carpaine. This substance has the usual properties of an alkaloid—combines with acids to form salts, and produces distinct physiological reactions. The dose of carpaine by hypodermatic injection is 1/6 to 1/18 of a grain, and by the stomach twice these quantities.

Thus far carpaine has been merely the subject of experimental investigation, and we need occupy but little space with an account of its physiological properties, the knowledge of which we owe to Van Ryn and C. L. Rümke. According to these investigators, who agree for the most part in their conclusions, carpaine is a cardiac remedy. It lowers the blood pressure, but increases the pulse rate but slightly. When the action of the heart is arrested by muscarin, it does not, like atropine, cause it to resume its movement when applied directly. It ultimately paralyzes respiration and circulation, but not by an impression made on the vagus. Its effects are really expended on the centers of respiration and circulation. It does not act on the peripheral nerves or on the muscles; it does not cause fibrillary trembling or tetanus.

Further investigations and clinical observations are necessary to determine the real place of carpaine as a remedy.