Dictionary.net

v[=a]'p[=o]-r[=o]l, n. a thin glass capsule, containing a volatile drug wrapped in cotton-wool and enclosed in a silk bag, to be crushed in the fingers so as to permit inhalation.

A glass capsule containing a single dose of a volatile drug.

Of Burroughs, Wellcome and Co., a friable glass capsule containing a drug to be employed for inhalation or fumigation, ensheathed in concentric layers of absorbent cotton, and the whole inclosed in a silken sack.