“On the chemical and physiological properties of ricin,” with demonstrations

A chemical study of the castor bean has indicated that this seed contains proteins of the same character as the other oil-seeds which have been examined, namely, (1) a considerable quantity of a globulin which can be obtained in octahedral crystals; (2) a much smaller quantity of an albumin, coagulating at about 60° C. to 70° C., the temperature at which it separates depending to a large extent on the rate of the heating and other conditions; (3) proteoses which appear to belong to several of the now recognized groups of this class of substances. The satisfactory separation of the various types of proteins was accomplished largely by the use of fractional salt precipitation and dialysis.

The toxic constituent of the castor bean has been investigated under Kobert's guidance by Stillmark, who applied the name ricin to protein material which he separated. The product which Stillmark regarded as relatively pure must have been a mixture of proteins and have contained only a small proportion of the toxic compound. Cushny made a more careful study of ricin and obtained a substance of sufficient toxicity to produce death in animals with a dose of 0.04 mg. per kilo of body-weight. He regarded the toxic compound as protein in nature. Among subsequent investigators, Jacoby has denied the protein character of ricin. He digested his toxic preparations with trypsin and obtained solutions which retained their toxicity although apparently no longer giving protein reactions. Brieger, however, failed to prepare toxic preparations free from protein material.

The efforts of the authors have been directed especially to the possibility of isolating the toxic constituent of the castor bean and determining its chemical nature. The toxic action has been found to be associated wholly with the preparations containing the coagu lable protein and never with those free from the albumin already mentioned