62 
The second and third toes have two perforated tendons ; one inserted into the sides 
of the first, and the other into the sides of the second phalanx. 
On a review of the details of the Muscular System above recorded, it will be seen 
that the analogies of the muscles on the dorsal aspect of the spine with those of Man 
and the Mammalia, are, in consequence of their unusually strong and distinct de- 
velopment in the Apteryx, more clearly traceable than their condition in other birds 
perhaps admits of. The same character of the muscles of the hind-extremity has led, 
as I believe, to a more accurate determination of them than had been adopted by former 
Comparative Anatomists, among whom the honoured names of Cuvier and Meckel call 
for a more detailed statement of the grounds on which I have ventured to dissent from 
views, so sanctioned, than has been given in the descriptive part of the present mono- 
graph. 
The chief modification of the skeleton of the hind limb of Birds, in respect of size and 
proportion, is manifested in its central segment ; the ossa innominata being anomalously 
expanded in order to include, as it were, in their grasp the whole of the very long sacrum 
required for the support of the horizontal trunk upon a single pair of extremities, The 
principal modification of the muscles of the leg attached to the ossa innominata might 
be expected, therefore, to be found in their origins. In the attachment of the fibres of 
a superficial muscle to the aponeurosis, continued from the outer part of the thigh, over 
the knee-joint, to the head of the tibia, we recognize the corresponding insertion of the 
tensor vagine femoris of Man and Mammalia; and no Comparative Anatomist appears 
to have thought the anomalous development and extensive origin of this muscle, in 
Birds, to be any objection to the homology indicated by its insertion, which is the at- 
tachment that mainly governs the function of a muscle. Now besides the attachment 
to the femoral fascia, we find this broad superficial muscle, and especially its middle 
and posterior fibres, terminating in a strong tendon, implanted into the upper part of the 
patella, and receiving fibres from the crureus and vasti muscles which it immediately 
covers, and with which it concurs in constituting a quadriceps extensor of the leg. Here, 
therefore, we perceive the normal insertion, the normal function, and the true relative 
position of the rectus femoris: and shall we reject these concordances on account of the 
modification of unusually extended origin? By parity of reason, we ought to reject the 
admitted homology of the tensor vagine ; and not only of this, but also of the sartorius and 
biceps cruris, both of which have undergone equal or greater modifications of origin in the 
class of Birds, It is true that the gluteus maximus is the most superficial of the outer 
muscles of the thigh in Man and Mammalia, and that it has the most extensive origin and 
largest size in Man ; but superior size and extensive origin are far from being the cha- 
racters of the gluteus externus in the lower Mammalia, in which it much more frequently 
