The Commens Dictionary
Quote from ‘The Basis of Pragmaticism’
…medium of communication is a species of medium, and a medium is a species of third. [—]
A medium of communication is something, A, which being acted upon by something else, N, in its turn acts upon something, I, in a manner involving its determination by N, so that I shall thereby, through A and only through A, be acted upon by N.
‘Medium of Communication’ (pub. 18.11.15-15:46). Quote in M. Bergman & S. Paavola (Eds.), The Commens Dictionary: Peirce's Terms in His Own Words. New Edition. Retrieved from http://www.commens.org/dictionary/entry/quote-basis-pragmaticism-17.