272 BACTERIOLOGICAL METHODS 



stances, when added to defibrinated blood in a test-tube, causes 

 clumping into a mass resembling sealing wax. The most im- 

 portant vegetable agglutinins are abrin, ricin, robin and crotin. 

 Of these, ricin, abrin and crotin also cause the coagulation of milk. 



To make the agglutination tests, defibrinated blood is used. 

 Whip the fresh blood (of ox, horse, guinea-pig or rabbit) by means 

 of twigs, bunch of thin wires, wire mesh egg beater, or run the 

 blood into Erlenmeyer flasks with iron filings and shake vigorously 

 for several minutes. The fibrin is deposited on the twigs, wires, or 

 on the iron filings, thus separating it from the corpuscles and the 

 serum. Removing the serum from the blood and displacing it by 

 physiological salt solution renders the reaction more pronounced, 

 thus pointing to the existence of antiagglutinins in the serum. 

 Ricin will agglutinate the blood of the guinea-pig in dilutions of 

 i : 600,000. Abrin, crotin and robin react in a similar manner. 



Saponins. These substances are widely distributed in the 

 plant kingdom and have chemical properties linking them with the 

 glucosides. They have been designated nitrogen-free glucosides. 

 The dry powder causes violent sneezing when inhaled and the 

 aqueous solutions foam when shaken. Most of them are neutral 

 in reaction and are capable of holding many finely divided sub- 

 stances in suspension. They dialyze with difficulty and incom- 

 pletely. They dissolve in hot as well as in cold water but are in- 

 soluble in absolute alcohol and in ether. 



Saponins have been found in many different species of plants. 

 The more important and better known are digitonin (in Digitalis 

 purpurea), saponin (Saponaria qfficinalis), githagin (Agrostemma 

 githago) , senegin (Poly gala senega} , saponin (Chlorogalum pomeri- 

 dianum), struthiin (Gypsophila struthium), sapotoxin (Quillaja 

 saponaria and Sapindus saponaria), and sarsaparilla-saponin 

 (Sarsaparilla species). Saponins are highly toxic when introduced 

 into the blood directly and some of them are well-known poisoning 

 agents. American Indians have long made use of the roots of 

 Chlorogalum for the purpose of stupefying fish. Most saponins 



