2IO On the Operation of Medicines. 



enter the blood. He forced a dog, which had 

 failed thirty-fix hours, to fwallow a pound of 

 bread and nnilk, with which an ounce and a 

 half of green vitriol were mixed. An hour 

 afterwards he opened the dog, and colleded from 

 the thoracic dud near half an ounce of chyle, 

 which aflumed no change of colour when the 

 tindure of galls was dropped into it ; though it 

 acquired a deep purple from the fame tindure, 

 when one fourth of a grain oi Jal martis had been 

 diflfolved in it. This experiment is ufually 

 deemed decifive in fupport of the theory, that 

 chalybeates exert their operations folely on the 

 ftomach ; and that the vigour they*communicate 

 to the fyftem arifes, exclufively, from their tonic 

 powers on the alimentary canal, and on the 

 fympathy of the ftomach with various other parts 

 of the body. I am not inclined to doubt either 

 the tonic adion or the fympathy fuppofed ; but 

 I fee-not that they preclude the immediate agency 

 of fteel on remote parts of the human frame. 

 For this remedy, in other forms capable of 

 being introduced, into the circulation, may exert 

 confiderable energy, as deobftruent, ftimulant, or 

 aftringent. And the experiment adduced only 

 evinces, that it did not fubfilt in the chyle as 

 a vitriol, qualified to llrike a black colour 

 with galls. Neither does the calx of iron, nor 

 the glafs of iron pofTefs this power : Yet, though 

 changed, they are both capable of being reftored 



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