From Francis Darwin   [15–18 September 1873]1

6QA

Dear Father

I asked Sanderson abt Mucin &c—2 there is a man who will be able to do it quite well, & he will naturally be making artificial gastric juice. Sanderson says Hæmoglobin is certainly indigestible but globulin ought to be, mucin does not turn into peptones like albumen does—3 I dont expect I shall come home before Sat

The dionœas went splendidly yesterday   we made observations all afternoon till 6.30   on one leaf we have made out some curious things quite satisfactorily4

Yrs affec | FD

CD annotations

Top of letter: ‘Take up substances’ pencil
1
The date range is established by the relationship between this letter, the letter to J. S. Burdon Sanderson, 14 September [1873], and the letter from Francis Darwin, [19 September 1873].
2
CD had asked John Scott Burdon Sanderson for small quantities of mucin, albumin, and fibrin (see letter to J. S. Burdon Sanderson, 14 September [1873] and n. 5).
3
CD was performing experiments to determine the ability of Drosera (sundew) to digest different substances. Globulins, albumins, haemoglobin, and mucin are all types of protein. Proteins that can be broken down by gastric juices form peptones, which are then absorbed. CD’s results on the digestive power of Drosera were published in Insectivorous plants, pp. 85–135.
4
Francis was assisting Burdon Sanderson with his experiments on Dionaea muscipula (Venus fly trap, see letter to J. S. Burdon Sanderson, 14 September [1873] and n. 2).

Please cite as “DCP-LETT-10156F,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-10156F