On Cutaneous Absorption. 293 



fourth, I employed considerable friction upon the lower 



extremities. 



EXPERIMENT V. 



In order to ascertain whether the colour of the urine 

 could be imitated, I made a saturated infusion of mad- 

 der in water. This was introduced guttatim into a 

 portion of clear water, until it acquired nearly the same 

 tinge with the urine. I then threw in a few drops of 

 the solution of the sulphat of iron ; the purplish-brown 

 was instantly visible. 



EXPERIMENT VI. 



Into a quantity of pale, recently-drawn urine, I dropt 

 the saturated infusion of madder, until the urine acquir- 

 ed precisely the same hue as the red urine of the fourth 

 experiment. The sulphat of iron, added to the urine 

 thus tinged, and to the urine of the fourth experiment, 

 produced the same purple-brown colour in each. This 

 experiment was repeated in the presence of my friend 

 Mr. French, and he declared that he could discover no 

 difference of colour in the two portions. 



EXPERIMENT VII. 



Doubtful whether the colour of the serum in the 

 fourth experiment could, with propriety, be referable to 

 the presence of madder, I took blood from my arm. 

 March 27, I found the serum of this blood considera- 

 bly redder than the former, but it had nothing of the 



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