Bullets. The N.E.D. gives an instance, ab. 1626, of “pills” in the same sense.

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1803.  Instead of boxing and bruising together, like sturdy Englishmen of the lower classes; or whipping one another through the lungs, with swords, or mutually injecting leaden pills, as has been common among the more polite and fashionable people.—The Balance, March 1, p. 65/2. (Italics in the original.)

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