204 LECTURES ON IMMUNITY 



observed in some experiments, whereas other experiments 

 executed with the same preparations and on the same day 

 (with the same horse blood) did not indicate the presence 

 of a prototoxoid. 



As illustration of ricin which does not show the 

 "protoxoid" zone, the following figures of Madsen and 

 Walbum l may suffice : 



n =o o.i 0.2 0.3 0.4 0.5 0.6 0.7 0.8 



?obs. =100 88 73 63 44 27.3 15.9 11.9 7.1 

 ?caic. =100 86 72 58 44 31.3 19.4 1 1.0 6.4 



Here the constant of equilibrium is only 0.014. Madsen 

 and Walbum found that the strength of the antiricin de- 

 creased continually, sinkiiig from the value I to 0.4 in 

 47 days and to 0.196 in 42 additional days, which corre- 

 sponds closely to a monomolecular reaction (cf. p. 37 ff.). 

 During the same time the constant of equilibrium dimin- 

 ished in the proportion 0.537 : 0.0142. 



The ricin has another toxic effect. On subcutaneous 

 injection it kills guinea-pigs, even if it is used in very 

 minute amount. Madsen and Walbum determined the 

 lethal dose to be 0.000123 g. The toxicity is therefore 

 expressed by the inverse number, 8130. Madsen and 

 Walbum took a quantity of poison 200 times less (40.7) 

 or 0.005 g. They added different quantities of anti- 

 ricin between o.oi and 0.035 c - c * t this quantity of 

 ricin, held the mixture for 20 minutes at 37 C. and injected 

 it thereafter into guinea-pigs. They found that the dif- 

 ferent mixtures contained the following number of lethal 

 doses : 



1 Madsen : British Medical Journal, Sept. 10, 1904, p. 9. 



