Having read Signor Menghini’s memoir, I recollected, that in the year 1753 I had, with the assistance of two friends, made the following experiment, in order to discover, whether iron, in a saline form, is capable of entering the lacteals. An ounce and a half of salt of steel dissolved in a sufficient quantity of water, filtrated and mixed with about a pound of bread and milk, were forced down the throat of a dog, that had been kept fasting for 36 hours. An hour after he had swallowed this mixture, having secured him in a supine posture, as is usual in such experiments, we opened the abdomen, and observed the lacteal vessels, like white threads, running along the mesentery in a very beautiful manner. Upon slitting open part of the small guts, we 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 struck a deep inky colour with infusion of galls. Tho’ the white colour of the lacteals convinced us, that they were full of chyle, yet, as it would have been impossible to have collected a sufficient quantity of it from them, we found it necessary to open the thorax, and tie the thoracic 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, we easily collected a sufficient quantity of chyle, and immediately mixed therewith, 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, tho’ they were rubbed together for some time, and allowed 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 I could guess, some what less than half an ounce, it is not to be imagined, that it could have failed to discover itself by this method of trial; for upon adding one fourth of a grain of the salt, this mixture instantly became of a bright purple: and I have found, by other experiments, that the smallest quantity of salt of steel shews itself as readily in the chyle by galls, as in any other liquor of the same consistence. This experiment (which was as fair as could have been desired), together with another observation I have 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_.