230 PHILOSOPHICA.L TRANSACTIONS. [anNO 1758. 



fix)m them, with regard to the action of iron on the human body, in such cases 

 as indicate its use, and where a rational physician would think proper to pre- 

 scribe it as a medicine. 



Having read Signor Menghini's memoir. Dr. W. recollected, that in the vear 

 1753 he had, with the assistance of 2 friends, made the following experiment, 

 in order to discover whether iron in a saline form is capable of entering the lac- 

 teals. An oz. and a half of salt of steel dissolved in a sufficient quantity of 

 water, filtrated and mixed with about 1 lb. of bread and milk, were forced down 

 the throat of a dog that had been kept fastmg for 36 hours. An hour after he 

 had swallowed this mixture, having secured him in a supine posture, as is usual 

 in such experiments, they opened the abdomen, and observed the lacteal vessels, 

 like white threads, running along the mesentery in a very beautiful manner. On 

 slitting open part of the small guts, they there found a good deal of the mixture, 

 which appeared frothy, but without any black colour, or the least sign of the 

 salt being precipitated ; and it struck a deep inky colour with infusion of galls. 

 Though the white colour of the lacteals convinced them that they were full of 

 chyle, yet as it would have been impossible to have collected a sufficient quantity 

 of it from them, they found it necessary to open the thorax, and tie the tho- 

 racic duct a little above the receptacle, which, from the ligature, soon became 

 turgid, the animal being alive and warm, and the chyle still continuing its course 

 towards the thoracic duct. Having cut open the receptacle, they easily collected a 

 sufficient quantity of chyle, and immediately mixed with it, drop by drop, infusion 

 of galls; a very simple and easy method, by which an incredibly small quantity of 

 salt of steel may be discovered in most liquors : but not the smallest change of 

 colour was observed, though they were rubbed together for some time, and al- 

 lowed to stand several hours. Now had there been a single atom, so to speak, 

 of the salt in so small a portion of chyle, as that used in this experiment, which 

 was, as near as he could guess, somewhat less than 4- oz., it is not to be ima- 

 gined that it could have failed to discover itself by this method of trial ; for on 

 adding ^ gr. of the salt, this mixture instantly became of a bright purple : and he 

 had found by other experiments that the smallest quantity of salt of steel shows 

 itself as readily in the chyle by galls as in any other liquor of the same consist- 

 ence. This experiment, with another observation he had made, viz. that neither 

 the blood nor urine of patients, during the use of salt of steel, in the least change 

 colour with galls, renders it more than probable that this salt does not enter 

 the blood. 



As the salt was found to have undergone no change in the small guts, it ap- 

 peared that it is not prevented from entering the lacteals by its being decomposed 

 or precipitated, as has been imagined ; but on the contrary, that what rendered 

 it incapable of being received by these vessels was its astringency : for the lac- 



