To J. S. Burdon Sanderson   31 March [1874]¹

My dear D^r. Sanderson.

How carefully & excellently you have made the experiments, which I fear must have cost you much trouble. They will be most useful to me, especially those on the acids & I am greatly obliged to you.² There is one point which you do not mention, & which I ought to know, viz the temperature at which the experiments were tried. Drosera digests at ordinary summer temperatures, & as far as casual observations serve almost equally well during ordinary summer weather & very hot weather. If you tried your experiments at the heat of human body or above that, it is just possible that the fatty acids would run a better race with the Hydrochloric at lower temperatures. Would it not be worth while to try one of the fatty acids & the Hydrochloric at ordinary temperatures?³

Again heartily thanking you | Yours very sincerely | Ch. Darwin

If all the globuline which I sent has not been used or thrown away,⁴ will you return me a few grains, as I sh^d like to try a few particles on Drosera aiding the plant with a minute drop of very weak Hydrochloric acid.—

P.S. I do not at present think that I shall try more digestion-experiments with Drosera this summer; not but what I like the work much, & your most kind offer is very tempting, but then I have other matter almost ready for publication & which, if I go on, I shall never have strength to publish.—⁵