To G. J. Romanes   5 June 1877

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

June 5. 1877

Dear Romanes,

I thought that you might like to see the following extract on which I stumbled by chance, as bearing on the effects of habit in the passage of nervous force.

Yours sincerely | Ch. Darwin

Lamarck Philosophie Zoolog

1830 Tome 2, p 3181

Dans toute action, le fluide des nerfs qui la provoque, subit un mouvement de déplacement qui y donne lieu. Or, lorsque cette action a été plusieurs fois répétée, il n’est pas douteux que le fluide qui l’a exécutée, ne se soit frayé une route, qui lui devient alors d’autant plus facile à parcourir, qu’il l’a effectivement plus souvent franchie, et qu’il n’ait lui-même une aptitude plus grande à suivre cette route frayée, que celles qui le sont moins.2

LS

1
Jean Baptiste Lamarck’s Philosophie zoologique was originally published in 1809 and reissued in 1830 (Lamarck 1809 and Lamarck 1830). CD’s copy of Lamarck 1809 is in the Darwin Libary–CUL (volume 1 only); it has the cover and title page of the 1830 edition (see Marginalia 1: 477–80).
2
The quotation from Lamarck 1830, pp. 318–19, may be translated as follows: In every action, the nerve fluid that excites it undergoes a movement of displacement that gives rise to it. Yet, when this action has been repeated many times, there is no doubt but that the fluid that performs it clears a path, which becomes all the more easy to traverse, which it has effectively crossed more often, and that it has a greater tendency to follow this open route, than those which are less so. Romanes was working on the nervous system of of medusae (see G. J. Romanes 1875, 1876, 1877a, and 1877b).

Please cite as “DCP-LETT-10983,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-10983