On Coloured Vision produced by Santonine. 93 



that, on being introduced into the system, it induces a mo- 

 mentary bilious condition, which passes off in the course of the 

 day. I also imagined, in my first experiment with Santonine, 

 that it induced a slight biliousness, but I neglected to observe 

 this in other experiments. In jaundice, as is well known, the 

 serum of the blood takes a yellow colour, and the urine be- 

 comes so yellow that it easily dyes a white cloth dipped into it. 

 Yet I have not heard it remarked that patients suffering from 

 jaundice, have ever seen objects otherwise than in their natural 

 colours. Leroy d'Etioles, lately one of the most eminent medical 

 practitioners in Paris, observed some time ago, that Santonine, 

 taken by children as a vermifuge, communicates to their urine 

 a greenish-yellow colour. I have also observed that Santonine, 

 or some substance derived from it, passes into the urine of 

 those who take it, and M. Miahle has made a similar observa- 

 tion.* Now, no substance can find its way into the urine 

 without passing through the blood. The presence of Santo- 

 nine, or any compound of Santonine, in the urine, is, therefore, 

 a proof direct that, in spite of its slight solubility in water, 

 Santonine is taken up, in some shape or other, by the blood, 

 and circulates through the system. The alkalinity of the blood 

 may facilitate its absorption, and it may be taken up as santo- 

 nate of soda, a tolerably soluble salt. But it is far more 

 probable that Santonine is transformed into a new substance, 

 of an intensely greenish-yellow colour, to which I gave the 

 name Santoneine, and obtained by boiling Santonine with nitric 

 acid. I believe this is the substance that passes into the 

 urine, and which forms on the crystals of Santonine by the 

 action of light. However, the chemistry of this product is 

 still very incomplete. Admitting that it gets into the blood, 

 as the greenish-yellow substance Santoneine, it is no longer so 

 difficult to account for the production of coloured vision. The 

 retina, or expansion of the optic nerve, is a translucid mem- 

 brane which receives numerous branches of the ophthalmic 

 artery, and sends a branch to the transparent vitreous humour of 

 the eye ; so that the ingestion of Santonine colouring the serum 

 of the blood, the latter is capable of colouring the transparent 

 media of the eye sufficiently to produce the effects described. 



In the present state of our knowledge of the chemistry and 

 physiology of Santonine, this appears to me the only manner 

 in which we can at all account for the production of coloured 

 vision, for Santonine does not appear to have any action what- 

 ever upon the nerves. 



* The urine of persons who have taken Santonine, evaporated to dryness, and 

 the residue treated with boiling alcohol, yields a solution which turns reddish- 

 orange when potassa is dropped into it, a character which serves to indicate 

 Santonine. 



