POISONOUS PLANTS 265 



In distinction to the majority of toxines — cf. snake venom 

 and bacterial toxines — ^ricine, like crotine, from Crdton tiglium, 

 is absorbed from the alimentary tract, probably by reason 

 of its resistance to decomposition by digestive enzymes. 

 But the poisonous dose by the mouth is at least one 

 hundred times as great as that by injection. The toxicity 

 of ricine is unknown and enormous. Impure preparations 

 may be purified by the action of trypsin, which destroys 

 accompanying albumins, the weight of ricine decreasing 

 without sensible diminution of toxicity.* Like other 

 toxines and ferments, ricine and its allies, crotine and 

 abrine (from Abriis precatorius), is destroyed by prolonged 

 heating over 60° C. in the moist condition, but is more 

 resistant to dry heat. 



The formation of ricine immunity is characteristic. 

 By increasing doses an animal may be made tolerant of 

 enormous normal overdoses of such magnitude as from 

 400 to 800 times, the tolerance not being due to habituation 

 of the tissues, but to the formation of a true anti-ricine in 

 the serum. The anti-body is capable of conferring immunity 

 on a second subject, and is specific against ricine, but not 

 against other toxines. 



The seeds of Croton tiglium resemble those of ricinus in 

 size and shape, but are dull brown in colour, and not 

 mottled. 



Those of Jatropha curcas, curcas purgans, or American, 

 Barbadoes, or purging nut, are not likely to cause poisoning 

 in Great Britain. 



Both croton and jatropha yield oils, and press residues, 

 and both are very dangerous. The mechanism of croton 

 poisoning is now known to be due to the toxine crotine, 

 whilst jatropha,^ according to Stillmark, contains ricine. 

 With croton is seems probable that in part the toxine 

 passes into the expressed oil. 



Symptoms. — Poisoning by ingestion of castor-oil beans, 

 or residues, does not declare itself, as a rule, till after several 

 days, and does not appear to be always marked by purga- 

 * See Oppenheimer, 'Toxines and Antitoxines,'- 1904, p. 165. 



