298 PROF. OWEN ON THE ANATOMY 



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 vagina femoris oi Man and MammaMa ; 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 femoi'al 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 crurceus 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 rccison, we ought to reject the 

 admitted homology of the tensor vaginre ; 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 glutceus externus in the lower Mammalia, in which it much more frequently 



