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Darwin Correspondence Project

To J. S. Burdon Sanderson   10 February 1875

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

Feb. 10. 75

My dear Dr Sanderson

Do you by any chance know whether animals can digest or decompose phosphat of potassium so as thus to obtain phosphorus? I ask because the phosphates of soda, lime, & ammonia act most powerfully on Drosera, wheras phosphate of potassium is as innocent as gum or sugar.1

I wrote some little time ago to Huxley, suggesting that Physiologists & Biologists should petition the H. of Commons to pass a reasonable act on vivisection, in the spirit of the Liverpool Brit: Assoc: resolutions.2 He said he would consult you; & I hope that you think well of the suggestion, & that something of the kind, or something better, will be done.3 I feel very anxious on the subject, for the sake of the grand Science of Physiology, & especially as an enactment advised by leading Physiologists would have much more influence on students & others.

Pray believe me | Yours very sincerely | Charles Darwin


CD described his experiment applying a solution of phosphate of potassium to leaves of Drosera rotundifolia (common sundew) in Insectivorous plants, p. 180. He did not specify what form of the compound was used.


Insectivorous plants. By Charles Darwin. London: John Murray. 1875.


Has been experimenting with phosphates on Drosera and wonders whether animals digest a particular one.

Asks whether Huxley has approached him regarding the introduction of a vivisection act.

Please cite as

Darwin Correspondence Project, “Letter no. 9849,” accessed on 31 July 2021,

Also published in The Correspondence of Charles Darwin, vol. 23