My dear D^r 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