CASTOR OIL, the fixed oil obtained from the seeds of the castor oil plant or Palma Christi, Ricinus communis, family Euphorbiaceae. The plant is a native of tropical Africa, but is cultivated in most tropical and warmer temperate countries. Be sides oil the seeds contain a powerful toxic substance (ricin) im portant as being, with abrin, the only vegetable substances to which antisera have been produced by immunological methods.
Much oil of excellent quality is obtained from India, Italy and California. The oil is obtained from the seeds by expression and decoction. One hundred pounds of good seeds may yield about five gallons of pure oil.
Castor oil is a viscid liquid, almost colourless when pure, with a slight odour, and a mild yet nauseous taste. Its specific gravity is 0.96 and it dissolves freely in alcohol, ether, and glacial acetic acid. It contains palmitic and several other fatty acids, but the chief is ricinoleic acid which occurs in combination with glycerin.
The active principle to which the oil owes its purgative proper ties has not been isolated. The dose is from a drachm to an ounce. By far the best way to administer the oil is in capsules, but it may be given in warm milk. It acts in about five hours, affecting the entire length of the bowel, but not increasing the flow of bile except in very large doses. The mode of its action is unknown.
The oil will purge when rubbed into the skin or injected per rec tum. It is an invaluable drug in temporary constipation and whenever a mild action is essential, as in pregnancy. It is useful for children and the aged, but must not be employed in cases of chronic constipation, which it only aggravates, whilst relieving the symptoms.