RICINE. 187 



of trypsin. Accordingly he modified his experiment in a very 

 ingenious fashion. 



Bicine is precipitated by ammonium sulphate on saturating 

 the solution to the extent of 60 per cent., whereas the active 

 principle of trypsin is not separated until the solution has been 

 completely saturated with ammonium sulphate. JACOBY, there- 

 fore, separated from an extract of pancreas by means of fractional 

 precipitation with ammonium sulphate the proteids that were 

 precipitated at a saturation of 60 per cent., and used this purified 

 trypsin preparation for the digestion of ricine that had been 

 separated by saturating its solution to the extent of less than 

 60 per cent. 



Hence this mixture, before the digestion, would have the 

 following composition : 



Precipitated at 60 per cent., . Ricine, and proteids com- 

 bined with it. 

 - 100 . Trypsin. 



After the action of the digestive enzyme, however, the composi- 

 tion would be different; the proteid impurities in the ricine 

 would have been digested by the trypsin, and would only be 

 precipitated with more difficulty by the trypsin, and possibly not 

 at all ; and the composition of the mixture would then be : 



Precipitated at 60 per cent., . Ricine. 



100 . Trypsin and part of the 



digested products. 



Under these conditions, then, the precipitation at a saturation of 

 60 per cent, must yield a pure ricine. 



As a matter of fact, JACOBY obtained only a very slight 

 precipitate by saturating the mixture to the extent of 60 per 

 cent, after a five weeks' digestion, and he purified this substance 

 by re-precipitation. 



The proteid reactions were no longer obtained, while the toxic 

 properties were quantitatively retained. Here, then, we have 

 proof that pure ricine is not a proteid. And this result also 

 disposes of one of the remaining " toxalbumins," and hence this 

 term may well be regarded as now only possessing historical 

 value. It has played an important part in the investigations of 

 this subject, especially since it led to the proof that these poisons 

 possessed quite different properties to the crystalloid poisons; 

 but surely the time has arrived for us to discard it, since now it 

 can only create confusion. In its place let us use the general 



