Nature of the Vesicating Constituent of Croton Oil, 249 



clear that the molecule is a very complicated one, and that the 

 empirical formula deduced from the analytical data must be doubled 

 at least and written CaeH^Os. With regard to the group of organic 

 compounds in which croton-resin should be included, the examina- 

 tion of its properties points to the conclusion, to be substantiated by 

 farther work, that, in all probability, it possesses the structure of 

 lactone or anhydride. It has already been shown that it has neither 

 basic nor distinctly acidic properties. It does not react with bisul- 

 phites or with phenylhydrazine, nor does it reduce Fehling's solution. 

 It is therefore not a ketone or an aldehyde. Attempts to form com- 

 pounds or derivatives of it by the action of various agents have not 

 been successful. It may be well to record here that auric chloride, 

 silver nitrate, mercuric chloride, lead acetate, cadmium iodide, iodine, 

 and picric acid do not react with an alcoholic solution of croton- 

 resin. 



The task of unravelling the constitution of this substance would be 

 a very difficult one if not an impossible one with our present know- 

 ledge, and the difficulty is greatly increased by the circumstance 

 that it is apparently incapable of being crystallised. The amount of 

 croton resin present in croton oil is small ; probably it does not 

 exceed 3 per cent. The extraction of the resin is not only a very 

 tedious and troublesome operation, but it is one not unattended with 

 danger to health. It attacks the mucous membrane and the skin 

 with great severity ; and we have evidence that when the body is 

 continually exposed to its action on one part or another — by contact 

 with the hand, or by the access of minute particles to the nose and 

 throat, as may occur during manipulation of the dry substance, or 

 during the evaporation of solutions containing it — the resin produces 

 a series of secondary effects which seem worthy of special study. 



It will be seen that our experiments have led us to a conclusion 

 opposed to that drawn by Buchheim, and more recently by Kobert 

 and Hirscheydt. We consider that we have disproved their conclusion 

 that the so-called "crotonoleic acid" is the vesicating constituent of 

 croton oil. Of previous workers Schlippe had obtained results most 

 in accordance with our own. He correctly suggested that the vesi- 

 cating constituent is not an acid ; and it is probable that the " crotonol " 

 obtained by this chemist chiefly consisted of croton-resin. 



In concluding this account of our work, the expenses of which have 

 been defrayed by a grant from the Royal Society out of the Govern- 

 ment Fund, we wish to express our obligations to the well-known 

 firm of Messrs. Horner and Sons, of Aldgate, for having furnished 

 us with freshly expressed oil of undoubted purity. The inquiry has 

 been conducted in the Research Laboratory of the Pharmaceutical 

 Society. 



VOL LIX. 



s 



