63 
manifests the proportions, as compared with the gluteus medius, which the muscle to 
which I have assigned the name of gluteus externus in the Apteryx, presents. But if the 
rectus femoris has undergone, as I believe, a similar modification of origin to that which 
characterizes the tensor vagine, sartorius and biceps, it would, by its extension along the 
spines of the sacrum, cover and mask the true gluteus eaternus, which arises from part 
of the outer surface as well as from the crista of the ilium ; and by the same modification 
of the rectus, that connection between the tensor and gluteus, which is present in some 
quadrupeds, would be severed ; while the more common close proximity of origin of the 
rectus and tensor is maintained. Already, in the Kangaroo, we find the origin of the 
rectus femoris extending from above the acetabulum higher up than usual upon the iliac 
bone. If, therefore, the great superficial muscle in question does not include the rectus 
femoris with the tensor vagine, then, with the evidence of the true gluteus externus in 
the muscle a Pl, XI. of the Apteryx, I should feel bound to regard it as an enormous 
development of the tensor vagine alone. 
Meckel assigns as his reason for regarding the muscle which I have called gluteus 
externus to be the gluteus medius, that its origin and relations to the other levators and 
abductors of the thigh are absolutely the same as the gluteus medius in Mammals*. It 
is, he says, covered by the gluteus maximus, meaning u Pl. X., or the great ‘ pyramidal ’ 
of Vieq. d’Azyr; but we are not bound to admit, in the absence of proof, the assump- 
tion that the great pyramidal of Vicq. d’Azyr is the gluteus maximus ; and until this be 
satisfactorily proved the argument is of no weight. I have already given reasons for re- 
garding the gluteus externus of Meckel as the combined tensor vagine and rectus femoris : 
the true gluteus externus is hidden in most birds, by the extraordinary extension of the 
origin of the rectus extensor cruris on one side, and of the biceps flewor cruris on the other ; 
but though covered, the gluteus ewternus is the outermost of the three glutci which are 
recognizable in the ‘ Apteryx.’ The more posterior position of its origin and its lower 
insertion, together with its inferiority of size as compared with the muscle which I have 
called gluteus medius, are characters which the gluteus externus of the Apteryx has in 
common with that muscle in most Mammalia, and especially in the genera Macropus and 
Dipus, which most resemble Struthious birds in the proportions and functions of their 
locomotive extremities. 
To attempt to conceive this muscle to be the homologue of the pyriformis involves so 
anomalous an inversion of position in respect of the pelvis, of relations to other muscles 
inserted into the proximal part of the femur, and of both origin and insertion, as can 
only be accounted for by the difficulty in which Cuvier, having recognized the true glu- 
teus medius, found himself in respect to the homologue of the gluteus externus, having 
applied the name of that muscle to the expanded tensor and rectus, by which it is covered. 
The remarkable concordance of the muscles of the rudimental wing in the Apteryx 
* Loc, cit. p. 352. 
