On Cutaneous Absorption. 289 



to them ? But to produce conviction on a mind cau- 

 tiously inquiring after truth, stronger evidence than is 

 furnished by analogy is often necessary ; and, on a 

 subject so important as the present, our opinions should 

 be fixed by experiment alone. 



Doubts respecting the existence of this long-acknow- 

 ledged function of the skin were raised by Mr. Seguin, of 

 Paris, and acquired great strength from the experiments 

 made in this city by Drs. Rousseau, Klapp, and Dain- 

 gerfield. These experiments, in which mercury and sti- 

 mulating odorous substances were the principal articles 

 employed, had labour, ingenuity, and candour to re- 

 commend them to the public, and induced many physio- 

 logists to renounce their former opinions on this point. 



It long since occurred to me, that coloured sub- 

 stances which are but moderately stimulating, and the 

 colouring part of which is known to be absorbed from the 

 intestinal canal, and to enter the circulation unchanged, 

 ought not to be neglected in the prosecution of an ex- 

 perimental inquiry into this subject ; and I resolved, 

 should no one anticipate me, to make some experi- 

 ments myself, when a convenient opportunity should 

 occur. Accordingly, March 22, 1809, I instituted a 

 course of experiments, with the Rubia tinctorum, or 

 Madder. 



EXPERIMENT I. 



I immersed myself, my head and anterior part of the 

 thorax excepted, in a pretty strong watery infusion of 



