Playfair was the member of Parliament for the Universities of Edinburgh and St Andrews.

See letter to Lyon Playfair, 15 May [1875].

Playfair had introduced a bill on the regulation of vivisection to the House of Commons on 15 May 1875; however, another bill on the same subject had been introduced in the House of Lords by Lord Hartismere (John Henniker-Major) on 4 May (see letter from J. S. Burdon Sanderson, [8 May 1875] and n. 3). A Royal Commission was appointed to gather information and report on the subject before legislation was drawn up (Hansard parliamentary debates 3d ser. vol. 224 (1875), col. 794). Edward Cardwell was chairman of the commission.

The first reading of the vivisection bill occurred when Playfair formally presented it in the House of Commons; the second reading would usually provide an occasion for debate, but in this case, because a Royal Commission was set up to look at the issues involved, it was a formality.