44 TOXINS AND ANTITOXINS. 



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 incon- 

 venience 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,* by Dixon, f 

 and Thuson.f 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. 



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 imme- 

 diate, 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. 



* Stillmark: Arbeit, aus dew. Pharmacol. Inst. Dorpat, 1889. 



t Dixon: Austr. Med. Gazette, 1887. 



X Thuson: Journ. f. prakt. Chem., xciv, p. 444. 



