The ill-disguised contempt with which Cuvier regarded these opinions may be exemplified by the following passage, taken from his Lectures on Comparative Anatomy: "If the ossa ilii have any relation with the scapula, the other two pelvic bones are very badly represented; whether it be that the clavicle is taken for the pubis, or for the ischium, as would be inferred from the inverse position of the two extremities; the trace of coracoid bone can hardly be taken into account. The marsupial apparatus of the marsupiata is never reproduced at the shoulder; very often the clavicle is wanting; the coracoid bone is reduced to a mere nothing, whilst the pelvis retains its three bones well developed. The articulation of the leg on the thigh is very different from that of the fore-arm on the arm, because the movements have become so altered j for the same reason the tarsus has but a very incomplete resemblance with the carpus, and this resemblance, slight as it is, vanishes altogether in birds, not only between the tarsus and the carpus, but between all the rest of the extremity, because their mode of standing, on the one hand, and the nature of their flight, on the other, demanded the conditions which were proper to them. What, moreover, becomes of the law of repetition in the Cetacea, who, for a pelvis, have no more than a rudimentary pubis; in the lamartins, the dugongs, the sirens, the apodous fishes, in whom there does not remain a trace of it ? Would the whole class of fish have been borrowed for this speculation, if the comparison had commenced from thence ? a class in which the anterior extremity is so complicated, and the posterior so simple, or, by an arrangement quite contrary to that of other vertebrata, in which the anterior extremity is firmly fixed to the trunk, whilst the posterior is so often simply suspended in the flesh. One sees, on the other hand, quite clearly, the reason of this disposition peculiar to fish, in the preponderating part which the anterior extremity, the pectoral fin, takes in the movement of swimming. In investigating the resemblances of the extremities, one has not to do with merely a vain law of repetition which their differences sufficiently refute; it is by this facility of generalising, without examination, propositions which are untrue but confined to a narrow circle, that it has been attempted to establish this law. These resemblances and differences are equally determined, not by the law of repetition, but by the grand and universal law of physiological concordance, and of the adaptation of means to an end."
Many of the objections here urged by M. Cuvier* have already been answered ; others seem rather unsatisfactory, coming from so accurate an observer, and so close and logical a reasoner. Why should the coracoid bone, stunted and coalesced with the scapula in man, be taken into less account than the fibula, stunted and coalesced to the tibia, or the ulna, stunted and coalesced to the radius in the horse, or in the deer ? The articulations of the knee and of the elbow bear a close resemblance to one another, and the homologies of the carpal and the tarsal bones can, without great difficulty, be determined. In the following table are arranged the homotypes of the bones forming the two extremities.
* Traite d'Anatomie comparee, vol. i., p. 342, 1835.