=Abrin.=--This toxin, which was studied in particular by Warden and Waddell,[52] then by Kobert[53] and de Hellin,[54] is found in the fruit of the Leguminosæ, Abrus precatorius (wild licorice, or jequirity). Its name was given it by Warden and Waddell, who discovered both its toxic nature and the vegetable toxin; the toxin is found only in the seeds. To extract it, the seeds are macerated in water, and the solution filtered and precipitated with alcohol; the precipitate which forms is collected and dissolved in distilled water, from which it is again precipitated by adding powdered ammonium sulphate. The precipitate is then collected and submitted to dialysis in order to eliminate the ammonium sulphate. The abrin so obtained forms an albuminoid substance[55] stable at 100° C., and possessing rotatory power; it liquefies starch paste, and is extremely toxic. One milligramme suffices to kill a rabbit within several hours. It must be observed, however, that, as is the case with all the toxins, abrin acts or kills only after a period of incubation which generally exceeds twenty-four hours. [52] WARDEN and WADDELL: _Non-bacillar Nature of Abrus Poison_. Calcutta, 1884. [53] KOBERT: _Arbeit. aus dem Pharmak. Institut._ Dorpat, 1893. [54] HELLIN: _Inaug. Dissert._ Dorpat, 1891. [55] EHRLICH: Experiment. Untersuchungen über Immunität. _Deutsch. Med. Woch._, 1891. It is possible to vaccinate an organism so as to withstand a lethal dose of abrin, but it requires quite a long time; it is effected by injecting into a suitable animal very small doses of the substance, and increasing the quantity gradually. Rabbits which have been rendered highly immune towards venoms are capable of resisting without inconvenience doses of abrin which are ordinarily fatal; and the blood serum afforded by them contains a specific antibody for the substance. =Ricin.=--This vegetable toxalbumin has been studied particularly by Stillmark,[56] by Dixon,[57] and Thuson.[58] It is found in the seeds of the castor plant; three or four of the seeds suffice to cause a gastroenteritis accompanied by serious symptoms and even by death. [56] STILLMARK: _Arbeit. aus dem pharmacol. Inst. Dorpat_, 1889. [57] DIXON: _Austr. Med. Gazette_, 1887. [58] THUSON: _Journ. f. prakt. Chem._, XCIV, p. 444. It was first isolated by P. Ehrlich, by treating the seeds with lukewarm water, and precipitating the aqueous solution with alcohol. The toxalbumin is soluble in water, but on boiling the solution, the substance loses in great measure its activity. Ricin possesses considerable activity. 0.00003 Gm. suffice to kill a rabbit when injected hypodermically; 0.2 Gm. are fatal to man. The action is not immediate, but follows a period of incubation. Ehrlich has shown that, exercising precaution, it is possible to create, as with abrin, a condition of tolerance or habituation, and in consequence to cause the formation of a specific antibody.