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Darwin Correspondence Project

From T. L. Brunton   2 December 1873

23 Somerset St. Portman Sq | London W.

Decr. 2nd. 1873

Dear Sir

Dr. Burdon Sanderson informs me that you are at present engaged with some experiments on the digestibility of chondrin & chlorophyll by Dionea.1 I have no reference at hand regarding the effect of the ordinary digestive fluids on chlorophyll & those on the digestibility of chondrin are not so accurate as I could wish. I shall be most happy to test the digestibility of both substances if you will let me know the form in which you have employed them so that I may use the same. I have digestive fluids & apparatus ready so that it will give me no trouble whatever— I was much interested lately by a photograph taken from the painting of the holy Mary of Egypt by Ribeia in the Dresden gallery.2 The painting strikes me at once by the decided squint which the painter has depicted. This excites the astonishment of every one as this extraordinary blemish does not detract from but rather adds to the beauty of the picture. On covering the sides of the face in the photograph alternately I observed that the expression of the two was quite different, that of the one being ecstatic & joyful that of the other repentant & sorrowful. On seeing this it occurred to me that when the painter wants to depict a very complex expression the two sides of the face will be almost necessarily different. The eye will express one, the mouth another or possibly more but if the whole face is to express more than the mouth & eye together, the two eyes & the two sides must differ. I have looked at one or two other photographs & noticed the same thing to a less extent— It is necessary to have very good photographs & the best are those taken from drawings by artists in Dresden. Very probably you have observed the same thing but I mention this because I do not remember any mention of it in your book on expression. I know that correspondence of any sort takes up much of any ones time and I do not wish to encroach upon yours which is so valuable but if you will merely write the names of the forms of chondrin & chlorophyll you use I will be glad to let you know their digestibility

Yours very truly | T Lauder Brunton

CD annotations

1.2 Dionea] underl pencil


CD had asked John Scott Burdon Sanderson to ask Brunton for information about the digestion of chlorophyll by animals, and also about gelatine and chondrin (see letter to J. S. Burdon Sanderson, 19 November [1873]). Chondrin is a protein–carbohydrate substance similar to gelatine that can be obtained by boiling cartilage in water; it is a constituent of commercial gelatine. Brunton had written on gelatine and chondrin in his chapter on the chemistry of tissues for the Handbook for the physiological laboratory (Klein et al. 1873, pp. 444–7).
The painting by Jusepe de Ribera, formerly thought to be of St Mary of Egypt, is now considered to be of St Agnes. It is in the Gemäldegalerie Alte Meister, Dresden.


Offers to experiment on the digestibility of chondrin and chlorophyll by Dionaea for CD.

Has noticed that painters depicting complex expressions give different expressions to the two sides of the face.

Letter details

Letter no.
Thomas Lauder Brunton, 1st baronet
Charles Robert Darwin
Sent from
London, Somerset St, 23
Source of text
DAR 160: 337
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9167,” accessed on 13 April 2021,

Also published in The Correspondence of Charles Darwin, vol. 21