The castor oil plant was cultivated by Albertus Magnus, Bishop of Ratisbon, in the middle of the 13th century.[2108] It was well known as a garden plant in the time of Turner (1568), who mentions the oil as Oleum cicinum vel ricininum.[2109] Gerarde, at the end of the same century, was familiar with it under the name of Ricinus or Kik. The oil he says is called Oleum cicinum or Oleum de Cherua,[2110] and used externally in skin diseases.
After this period the oil seems to have fallen into complete neglect, and is not even noticed in the comprehensive and accurate Pharmacologia of Dale (1693). In the time of Hill (1751) and Lewis (1761) Palma Christi seeds were rarely found in the shops, and the oil from them was scarcely known.[2111]
In 1764 Peter Canvane, a physician who had practised many years in the West Indies, published a “Dissertation on the Oleum Palmæ Christi, sive Oleum Ricini; or (as it is commonly call’d) Castor Oil,”[2112] strongly recommending its use as a gentle purgative. This essay, which passed through two editions, and was translated into French, was followed by several others,[2113] thus thoroughly drawing attention to the value of the oil. Accordingly we find that the seeds of Ricinus were admitted to the London Pharmacopœia of 1788, and directions given for preparing oil from them. Woodville in his Medical Botany (1790) speaks of the oil as having “lately come into frequent use.”
At this period and for several years subsequently, the small supplies of the seeds and oil required for European medicine were obtained from Jamaica.[2114] This oil was gradually displaced in the market by that produced in the East Indies: the rapidity with which the consumption increased may be inferred from the following figures, representing the value of the Castor Oil shipped to Great Britain from Bengal in three several years, namely 1813-14, £610; 1815-16, £1269; 1819-20, £7102.[2115]
Description—The fruit of Ricinus is a tricoccous capsule, usually provided with weak prickles, containing one seed in each of its three cells. The seeds attain a length of ³/₁₀ to ⁶/₁₀, and a maximum breadth of ⁴/₁₀ of an inch, and are of a compressed ellipsoid form. The apex of the seed is prolonged into a short beak, on the inner side of which is a large tumid caruncle: from this latter proceeds the raphe as far as the lower end of the ventral surface, where it forks, its point of disappearance through the testa being marked by a minute protuberance. If the caruncle is broken off, a black scar, formed of two little depressions, remains.
The shining grey epidermis is beautifully marked with brownish bands and spots, and in this respect exhibits a great variety of colours and markings. It cannot be rubbed off, but may after maceration be peeled off in leathery strips. The black testa, grey within, is not thicker than in croton seed, but is much more brittle. The kernel or nucleus fills the testa completely, and is easily separated, still covered by the soft white inner membrane.
The kernel in respect to structure and situation of the embryo, agrees exactly with that of Croton Tiglium ([p. 565]), excepting that the somewhat gaping cotyledons of Ricinus are proportionately broader, and have their thick midrib provided with 2 or 3 pairs of lateral veins. If not rancid, the kernel has a bland taste, with but very slight acridity.
Microscopic Structure—The thin epidermis consists of pentagonal or hexagonal porous tabular cells, the walls of which are penetrated in certain spots by brownish colouring matter, whence the singular markings on the seed. It is these cells only that become blackened when a thin tangential slice is saturated with a solution of ferric chloride in alcohol.
Beneath these tabular cells there is found in the unripe seed[2116] a row of encrusted colourless cells, deposited in a radial direction on the testa. In the mature seed this layer of cells is not perceptible, and therefore appears to perish as the seed ripens. The testa itself is built up of cylindrical, densely packed cells, 300 to 320 mkm. long, and 6 to 10 mkm. in diameter. The kernel shares the structure of that of C. Tiglium, but is devoid of crystals of oxalate of calcium. If the endopleura of Ricinus is moistened with dilute sulphuric acid, acicular crystals of sulphate of calcium separate from it after a few hours.
When thin slices of the kernel are examined under concentrated glycerin, no drops of oil are visible, notwithstanding the abundance of this latter; and it becomes conspicuous only by addition of much water. Hence it is probable that the oil exists in the seed as a kind of compound with its albuminoid contents.[2117] As to the latter, they partly form in the albumen of Ricinus beautiful octohedra or tetrahedra, which are also found in many other seeds.[2118]