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Darwin Correspondence Project

From J. S. Burdon Sanderson   19 June 1874

The Brown Institution, | Wandsworth Road, S.W.

June 19th. 1874

Dear Mr. Darwin,

I enclose a bit of cartilage of the external ear of the cat which from containing elastic fibres will probably resist digestion considerably.1 I have just put the cartilage of the other ear into ordinary digestive liquid in the warm chamber. I have directed my man to procure this evening and send you some proper fibro-cartilage i.e. cartilage of which the fibrous tissue is gelatigenous. I should expect that that would be digested easily.2 The cartilage that will be sent will be that of the symphysis pubis3

Some days ago I sent you in a railway parcel a little box containing the three volatile acids4 & a specimen of fibrin. I hope they arrived safe. All that the fibrine requires in order to make it fit for use is to wash it in ordinary water, so as to get rid of the glycerin in which it is now contained. It can be kept in the glycerin for an indefinite period without change.

I am very sorry that we have neglected so long your experiment on enamel. I have put some into the chamber this afternoon, in a quantity of digestive liquid.5

Very truly yours | J S B Sanderson


CD was testing the digestive ability of Drosera (sundew) on different substances. He described the partial digestion of the cartilage from the cat’s ear in Insectivorous plants, p. 104.
Burdon Sanderson’s assistant was Frederic James Montague Page. Contrary to Burdon Sanderson’s expectations, CD found that the fibrocartilage became hyaline but was not dissolved (Insectivorous plants, p. 104).
The symphysis pubis is the midline cartilaginous joint between the right and left pubic bones in mammals. In Insectivorous plants, p. 104, CD described the cartilage as coming from between the vertebrae of the tail of a sheep.
Volatile acids are those easily vaporised, such as the carboxylic acids. In Insectivorous plants, pp. 89–91, CD discussed experiments made by Burdon Sanderson using propionic (now often referred to as propanoic), butyric, and valerianic (now valeric or pentanoic) acids, all of which are carboxylic acids.
CD reported the initial results of his experiments on Drosera (sundew) with dentine and enamel in his letter to J. S. Burdon Sanderson, 5 May [1874]. In Insectivorous plants, p. 108, CD noted that he asked Burdon Sanderson to try bone, enamel, and dentine in artificial gastric juice. No letter making this request has been found, but Edward Emmanuel Klein mentioned in his letter of 14 May 1874 that Burdon Sanderson planned to make experiments to determine the action of gastric juice on ‘tooth-substance’ (presumably dentine).


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.]

Letter details

Letter no.
John Scott Burdon Sanderson, baronet
Charles Robert Darwin
Sent from
Brown Institution
Source of text
DAR 58.1: 60–1
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9502,” accessed on 22 March 2019,

Also published in The Correspondence of Charles Darwin, vol. 22