Full Idea
All things possess quantity; consist of parts which can be numbered; and in that character possess all the properties which are called properties of numbers.
Gist of Idea
Things possess the properties of numbers, as quantity, and as countable parts
Source
John Stuart Mill (System of Logic [1843], 2.6.2)
Book Reference
Mill,John Stuart: 'System of Logic (9th ed, 2 vols)' [Longmans, Green etc 1875], p.293
A Reaction
Here Mill is skating on the very thinnest of ice, and I find myself reluctantly siding with Frege. It is a very optimistic empiricist who hopes to find the numbers actually occurring as properties of experienced objects. A pack of cards, for example.