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Darwin Correspondence Project

From George Busk   10 March 1871

32 Harley St

Mar 10/71

My dear Darwin

As it seems to me that you have fallen into some misapprehension with respect to the supra condyloid foramen in the human Subject (p. 28) I hope you will not take it amiss if I call your attention to the point.1

The true supra condyloid foramen or more properly canal, as it exists in the Felidæ and some other animals is formed by a process or bridge of bone extending from the internal condyloid ridge to the epicondyloid eminence and thus forming a canal through which the median nerve & in some cases an artery and veins pass, whilst the operus bridge itself affords an additional surface for the origin or attachment principally of the pronator teres muscle.2 It may therefore be regarded as of some functional importance, but that it has no genetic significance3 seems tolerably clear seeing that it occurs in a variety of animals belonging to widely different orders and families, but all, animals more or less distinguished either as active carnivores with powerful talons, such as the Felidæ—or as diggers & burrowers—as the Mole Badger Weasles—Anteaters &c; or as swimmers as the Otter & Common Seal; or as active climbers, as some few tailed monkeys Lemurs (I believe) Loris, Tarsius4 &c—all animals whose habits demand great powers of pronation & flexion in the fore paw. It is not improbable that in the Marsupials so many of which possess this canal it may have some genetic significance, but I think that even in them also it will be found to be more of a functional character.

In the human subject this operus bridge is represented by an intermuscular tendinous or aponeurotic band occupying the same position & in like manner affording origin in part to the pronator teres muscle & to one of the carpal flexors. And it would seem that in some rare instances this band may become partially or entirely ossified, when it would represent both functionally & morphologically the osseous process of the Felidæ &c. Its occurrence therefore in Man would not appear to be of any morphological importance; and would merely serve to indicate that the individual, had, in all probability and unusually well developed pronator teres &c. Whether this would give any advantage in the struggle for existence I cannot say—but I should apprehend that it has not yet done so, since the occurrence of the canal in Man is extremely rare, and has not, so far as I know, been observed to prevail in any particular race of Mankind.

The supra condyloid perforation referred to in my Account of the Gibraltar Caves and noticed by M. Broca in the quotation you cite is a totally different thing, and if possible of still less importance in any point of view.5 The perforation is produced simply by a deficiency of bone at the bottom of the olecranon-fossa at the point where the septum between that fossa & the Coronoid fossa in front is naturally little thicker than paper. Of course as this perforation is in the middle of the articulation & within the capsule of the joint no vessel or nerve can pass through it—so that it has neither functional nor morphological significance— It is constant I think in some animals but in most it appears to be of only occasional or accidental occurrence as in Man; and it may exist on one side & not on the other as in the instance of the opposite humeri of U Spelæus from Gaylenreuth in the College Museum.6

In some instances, however, as in the caves in Algeria explored by Genl Faidherbe and M. Bourgignat the perforation may occur in such a large proportion of the ursine humeri, as almost to justify its being regarded as a race character, though certainly not of specific importance as it has been considered by M. Bourgignat in his Ursus Faidherbianus.7 How far it may indicate affinity of race in the human subject as in the Guanches, Bushmen & the priscan people noticed by M. Broca I cannot say.8

I have enclosed a fragment of the humerus of a Rabbit showing the perforation referred to by M. Broca & myself & also a figure of the humerus of U. Spelæus to which I have alluded, and if you compare these with the humerus of a Cat or Badger &c—you will at once see that it has no relation whatever to the supra-condyloid foramen or canal

Yours very truly | Geo: Busk



perforated humerus

Ursus Spelæus


CD annotations

On cover: ‘Condyloid Foramen | Ascertain in how many of the Anthropomorphous apes—is there a fairly well developed supracondyloid process’ ink


Busk refers to Descent 1: 28. George Rolleston had already pointed out CD’s error (see letter from George Rolleston, 22 February 1871 and n. 3).
The pronator muscles in humans are in the forearm.
Busk uses the word ‘genetic’ in the sense of ‘developmental’.
Lemurs, lorises, and tarsiers (genus Tarsius) are primates of the families Lemuridae, Loridae, and Tarsiidae respectively.
See Descent 1: 28–9. Busk refers to Busk 1868 and to Paul Broca. CD’s annotated copy of an offprint of Busk 1868 is in the Darwin Pamphlet Collection–CUL. In Descent 2d ed., p. 22, CD retained the reference to Busk 1868, but revised the section to reflect more accurately Busk’s account.
Bones of Ursus spelaeus, the cave bear, found in the caverns at Gaylenreuth near the river Wiesent in Germany, were held in the museum of the Royal College of Surgeons, London.
Busk refers to Louis Léon César Faidherbe and Jules René Bourguinat. Ursus faidherbianus (now U. arctos faidherbianus), is an extinct North African bear species. For Bourguinat’s description of the humerus of this bear, see Bourguinat 1867, p. 50.
In Busk 1868, p. 54 n., Busk discussed the perforation of the humerus above the condyles in the bone of a Bushwoman and speculated about the relative frequency of the feature in early humans. A section of the footnote has been excised in CD’s copy. The ‘Bushmen’ are indigenous people of southern Africa, now more commonly referred to as San in South Africa and by a variety of other names in different countries. The Guanches were the indigenous people of the Canary Islands (EB). Priscan: ancient, primitive (OED).
Royal College of Surgeons.


Busk, George. 1868. On the caves of Gibraltar in which human remains and works of art have been found. Transactions of the International Congress of Prehistoric Archaeology 3d session (1868): 106–66.

Descent 2d ed.: The descent of man, and selection in relation to sex. By Charles Darwin. 2d edition. London: John Murray. 1874.

Descent: The descent of man, and selection in relation to sex. By Charles Darwin. 2 vols. London: John Murray. 1871.

EB: The Encyclopædia Britannica. A dictionary of arts, sciences, literature and general information. 11th edition. 29 vols. Cambridge: Cambridge University Press. 1910–11.

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.


Clarification of the supra-condyloid foramen in humans and animals.

Letter details

Letter no.
George Busk
Charles Robert Darwin
Sent from
London, Harley St, 32
Source of text
DAR 87: 21–7
Physical description
9pp † encl 2pp

Please cite as

Darwin Correspondence Project, “Letter no. 7563,” accessed on 2 July 2020,

Also published in The Correspondence of Charles Darwin, vol. 19