From F. C. Donders 12 July 1874
Marienbad (Bohemia)—
12 July 1874.
My dear Mister Darwin.
As your son George, whom I was very happy to see, told me of your experiments on Drosera, I, in fact, mentioned the great sensibility of the muscular fibres of the iris for atropine.1
It is 25 years ago that I made experiments on this point, with one of my pupils (Dr. de Ruyter)2 and I repeat a part of them every year on my lectures.
The question was, whether the atropine (sulphate of atropine has been used)3 acts directly or indirectly on the iris. We found, that it is a direct action. Small doses act only by application on the cornea, and the atropine is transported into the eye by imbibition. We applied repeatedly on the cornea of a rabbit a solution of 1 to 100 water, washed thoroughly out the conjunctival sac with a stream of water, evacuated by a punction4 the aqueous humour and put it in the eye (on the cornea) of a dog, whose iris is very sensible to atropine: it really produced a notable dilatation of the pupil for some hours.
The question now was this, how much atropine the aqueous humour of the rabbit contained. By comparing with a series of dilutions of our normal solution, we found, that a solution of 1 to 100000 acts as much on the dog’s eye as the aqueous humour of the rabbit’s eye, after the application of 1 to 100.— We conclude, that after an application of 1 to 100, the real acting solution (the aqueous humour) is at 1 to 100,000. Now, after an instillation of 1 to 100000, the acting solution may be of 1 to 100,000000. Of course, the action continues for a certain time, and whilst some particles are absorbed by the internal vessels, other arrive from the cornea into the aqueous. But certainly, we go not too far, if we admit, that alltogether not 1:1.000000 of a grain enters and acts on the iris, and that the acting solution contains, ad maximum,5 less than 1 to 10.000000
And still, we know, that the dog’s iris is a rather large organ.— Perhaps I can send you a copy of de Ruyter’s dissertation, written in Latin, as soon as I am back in Utrecht.6
You are aware that the action of atropine is chiefly paralysing (perhaps irritant on the radiary fibres). Irritant, in the sense of phosphate of Ammonia, is the action of Physostigmine (from the Calabar bean, Physostigma venenosum),7 but it seems to me, that it is not quite so active in minimal doses as the atropine: I did not determine it in numbers.
Perhaps the sensibility of the anterior grey substance of the medulla spinalis8 of the frog for the direct application of strychnine9 (producing tetanus in the corresponding muscles) is as great as that of atropine on the Iris
Professor Engelmann, my son in law, published a book on the influence of several substances, especially of vapours and gazes, on vibratile motion, on the motions of spermatozoids of protoplasma etc. and I remember that he found a wonderfull sensibility for some of them. He will be very happy to be allowed to send you a copy (in German), after having had the opportunity to signalise in the copy the facts, which may be of some importance to you.10
I was very happy to hear from your son, that your health is tolerably good, and it was quite an honour and a pleasure to me to receive your letter. Here I had nothing better to do than to answer immediately. Most willingly I will supply to you afterwards a more complete account of the facts, if you want it.
Pray, believe me with the highest esteem | Yours very sincerely | Donders.
addresse: | Prof. D., zum | Telegrafen, | Marienbad.
CD annotations
Footnotes
Bibliography
Engelmann, Theodor Wilhelm. 1868. Über die Flimmerbewegung. Leipzig: Wilhelm Engelmann.
OED: The Oxford English dictionary. Being a corrected re-issue with an introduction, supplement and bibliography of a new English dictionary. Edited by James A. H. Murray, et al. 12 vols. and supplement. Oxford: Clarendon Press. 1970. A supplement to the Oxford English dictionary. 4 vols. Edited by R. W. Burchfield. Oxford: Clarendon Press. 1972–86. The Oxford English dictionary. 2d edition. 20 vols. Prepared by J. A. Simpson and E. S. C. Weiner. Oxford: Clarendon Press. 1989. Oxford English dictionary additional series. 3 vols. Edited by John Simpson et al. Oxford: Clarendon Press. 1993–7.
Ruiter, Gerardus Cornelius Petrus de. 1853–4. Onderzoekingen over de werking van Atropa Belladonna op de iris. Nederlandsch Lancet (1853–4): 434–72.
Ruiter, Gerardus Cornelius Petrus de. 1853. Dissertatio physiologico-medica de actione atropae belladonnae in iridem. Utrecht: P. W. van de Weyer.
Summary
On hearing of CD’s work with Drosera, tells of his experiment showing extreme sensitivity of the iris of a dog’s eye to atropine. [See Insectivorous plants, p. 173.]
Letter details
- Letter no.
- DCP-LETT-9545
- From
- Frans Cornelis (Franciscus Cornelius) Donders
- To
- Charles Robert Darwin
- Sent from
- Marienbad
- Source of text
- DAR 58.1: 79–80
- Physical description
- ALS 4pp †
Please cite as
Darwin Correspondence Project, “Letter no. 9545,” accessed on 28 March 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-9545.xml
Also published in The Correspondence of Charles Darwin, vol. 22