PHYTOTOXINS 167 



with the coagulable albumin of the castor beans, and were able 

 to isolate it in such purity that one one-thousandth of a milli- 

 gram (0.000001 gram) was fatal per kilo of rabbit, and solutions 

 of 0.001 per cent, would agglutinate red corpuscles. The toxic- 

 ity was also impaired or destroyed by tryptic digestion. They 

 consider that probably, because of its extremely great toxicity, 

 Jacoby was able to get active preparations that contained too 

 little active substance to give the proteid reactions. As they 

 remark : " If one-thousandth of a milligram of a compound 

 giving on analysis every indication of being a relatively pure 

 protein, is physiologically active in the degree characterized by 

 our experiments, the toxicity of any impurity must be infinitely 

 greater than that of any known toxins." In this connection 

 may be mentioned the ultra-microscopic studies of tetanus anti- 

 toxin quoted by v. Behring L which showed that by dialysis a 

 solution containing active antitoxin could be obtained giving 

 none of the reactions for proteids, yet by ultra-microscopic 

 methods it could be demonstrated that proteids were present. 

 Against the claim that the toxic principle is simply carried down 

 with the proteid is the fact that it does not come down in the 

 first fraction that is precipitated, the globulin, which usually 

 carries down all impurities. All the ricin comes down between 

 the limits of one-fifth and one-third saturation with ammonium 

 sulphate, exactly as does the albumin. 



Immunity. The phytotoxins have been very servicable in 

 the study of immunity, since they obey the same laws as 

 bacterial toxins and can be handled in more definite quantities. 

 By their use Ehrlich first determined that toxin and antitoxin 

 act quantitatively. They seem to possess haptophore and tox- 

 ophore groups, and immunity is readily obtained against them, 

 not only by subcutaneous injection, but by dropping into the 

 conjunct! val sac, and also by feeding, showing their direct absorb- 

 ability and their resistance to digestion. The antitoxin is present 

 in the milk of the immunized mother and immunizes the suckling ; 

 but little is carried through the placenta into the fetal blood. 

 The immunity is specific, ricin antitoxin, for example, not pro- 

 tecting against abrin (although it is said to protect against 

 robin). Roemer found that in animals immunized by conjunctival 

 application the eye so used became immune to the local action 

 of the poison before the other eye did, indicating a local develop- 

 ment of immune substance. In general immunization the 

 immune substance appears first in the spleen and bone-marrow. 

 Normal serum gives a precipitate with ricin, but immune serum 

 1 Beitr. exp. Therapie, 1905, H. 10, p. 22. 



