To J. S. Burdon Sanderson   21 June [1874]¹

My dear D^r. Sanderson

I have received & am heartily obliged for the acids, the fibrin & 2 spec. of fibro-cartilage.— You do not know how valuable the fibrin has proved; both Drosera & Pinguicola have quickly dissolved every atom; so that I sh^d. have fallen into a grievous error & said that neither could wholly dissolve fibrin: no doubt what I saw left undissolved was impurity in the wretched fibrin which I before employed.² Thus one great & horrid anomaly is removed. But there remains another, (if I understand rightly), viz that artificial digestive fluid dissolves the fibrous basis of decalcified bone.³ If this is so I must try Drosera again, as it is just possible that D. would not attack the tissue until it had removed every atom of the Phosphate & all free animal matter. The second anomaly is about gluten: I prepared it myself by washing it in water till I got very viscid pale brown substance; but there may have been some starch left, & how I am to ascertain this I know not.—⁴

I have just read with very great interest your 2^d article on Dionæa: it is most wonderful that there sh^d. be that identity between muscle & a leaf.—⁵ I fear that you misunderstood me on the point: the aggregation of the protoplasm does not occur until sometime after the movement has occurred.⁶ But to look closer to this point has been a subject on my list for closer observation for some little time. Again aggregation occurs with no movement ensues, as when too strong a dose (viz 2 or 3 gr. of carbonate of A. to 1 oz) is given.—⁷

I do not think I expressed in my last note how very much I was pleased by your very honourable & encouraging notice of my work.⁸

Yours most sincerely | Ch. Darwin

P. S. Your man has made an odd mistake & has sent me vertebral bones with no cartilege; but Frank has now come home, & knows fibro-cartilege, & will get me some from a joint or from the Butchers’.—⁹