Informs CD of the effects of certain salts and other chemicals on animals.

Comments on CD’s results with Drosera. Suggests some experiments.

A hasty answer to CD’s letter [8987] of 25 July. Mentions Dr Osler’s observations on behaviour of colourless blood corpuscles in solutions of sodium and potassium salts of same strength.

Answers CD’s questions of 25 July [8987] about temperatures at which cold-blooded animals are killed.

Doubts heat rigor was induced in Drosera. Gives his view of the relation of excitability to increase in temperature.

Suggests experiment to show that electrical changes in plant are the same as in animal muscle and nerve [see Insectivorous plants, p. 318].

Sends results of experiments on digestion. Encloses two sets of notes: "Experiments on the digestibility of certain preparations sent by Mr Darwin" and "Note for Mr Darwin" [marked by CD for insertion in ch. 6 of Insectivorous plants].

Purpose of experiments was to determine digestive activity of liquids containing pepsin. Gives required amounts of hydrochloric, propionic, butyric and valerianic acids. Describes experiment and gives results. Also experimented on digestive activity of butyric acid at greater temperatures than the termperature of the body.

Reports results of experiments comparing digestibility of gluten and fibrin for CD’s work on Drosera.

Sends CD provisional information that artificial gastric juice dissolves bone entirely and that gluten and fibrin are completely dissolved in hydrochloric, propionic, and butyric acids. [See Insectivorous plants, pp. 118–19.]

Sends cartilage from cat’s ear, the elastic fibres of which will probably resist digestion [by Drosera]. Is preparing fibro-cartilage, which he expects will be digested easily. [See Insectivorous plants, p. 104.]

Is delighted to hear that Pinguicula and Drosera digest fibrin. Suggests diluting gluten in weak hydrochloric acid to remove starch. Enamel was nearly digested [by Drosera] overnight. Would like to try separating the digestive ferment of Pinguicula.

Will prepare experiments with the fatty acids on digestion of gluten. Has found it is digested slowly, but entirely, with pepsin and hydrochloric acid.

Suggests an explanation for difference in excitability of Drosera leaves to meat and albumen on the one hand and, on the other, fibrin, areolar tissue, gelatin, and fibrous basis of bone.

Responds to CD’s questions about relation to gelatin of areolar tissue, fibrous basis of bone, and other substances CD is using in his work on digestion of Drosera.

Thanks CD for a copy of Erasmus Darwin.