160 COUES ON THE OSTEOLOGY 



prominent and convex, with a deep sulcus between them. They much resemble, in general 

 appearance, the condyles of the human femur ; but are laterally more compressed, and the 

 sulcus between them is wider. It is remarkable that the internal one is the largest and 

 longest, so that the obliquity of the tibia in relation to the axis of the body, instead of 

 being corrected in the metatarsus, is increased, and the foot thrown still further outwards. 

 On the posterior aspect, the condyles continue upwards for some distance, as prominent 

 narrow ridges, serving to confine the very numerous tendons which pass down over the 

 heel. The sides of the condyles are rough for ligamentous attachment. Just above the 

 condyles, on the anterior face of the bone, is the depression ordinarily met with, crossed by 

 a very distinct though small bridge of bone, forming a canal through which the extensor 

 tendon of the toes passes. 



Fibula. This is as usual a tapering bone, not extending the whole length of the tibia, and 

 attached to its outer and somewhat posterior aspect. Its head is quite distinct, lying just 

 at the edge of the head of the tibia, receiving the greater part of the outer condyle of the 

 femur. For an inch or so, it is quite separate from the tibia; is then united with it for 

 some distance, becomes again distinct for about an inch, and then finally merges as a slender 

 spiculum into the side of the tibia, rather more than an inch above the joint, ° A slight crest 

 however, gives an indication of it, which can be traced quite to the external malleolus of 

 the tibia. 



« Tarso-metatarsus." The next segment of the lower extremities results, as in most if not 

 all birds, from the fusion of the elements of the tarsus and metatarsus proper. 1 In this 

 species it is an exceedingly compressed bone three and a half inches in length ■ its sides 

 nearly smooth and quite flat; its anterior and posterior borders grooved for°the' reception 

 respectively of the extensor and flexor tendons ; and separated from the sides by remark- 

 ably sharp edges. These edges are so prominent that they impress a very decidedly rec- 

 tangular shape upon a transverse section of the shaft of the bone. By these Grooves and 

 the fibrous thecae, which their sharp edges give origin to, the tendons are prevented from 

 encroaching in the least on the sides of the tarsus, which is thus enabled to keep its ex- 

 ceeding thinness ; while at the same time they serve to increase greatly the antero-posterior 

 width of this segment of the le°\ 



The process of bone representing the os calm, rises at the superior end of the bone on 

 its posterior aspect, as a very conspicuous crest. It is of quite a regular square shape 

 about a third of an inch long, and of about the same height. The groove denoting its line 

 of fusion with the metatarsus may be traced along its base. Into it are inserted the two ten- 

 dons of the gastrocnemii ; and its substance is perforated by longitudinal canals, through 

 which pass the flexor tendons of the toes. The most posterior of these canals is very lame 

 and transmits the majority of these tendons ; anterior to it, that is between it and the meta- 

 tarsus, are two or three very small canals, lying side by side on the same plane 



The proximal extremity of the bone is marked on each side of the median line by two 

 oval depressions m which are received the condyles of the tibia. In shape and position the 

 two differ slightly from each other, in consequence of a corresponding difference in the two 

 condyles of the tibia. On either side of the head are the roughened elevations for ligamen- 

 tous attachments, and for the tendons of the tibialis posticus and peroneal muscles 



I he metatarso-phalangeal articulation is extremely interesting. If we examine the foot of 



the " ItT l^oLh •t h0l ° SiCa ' Wr ; eR " T erSa " y Ca " ed banll - V W °'-' h whiIe ,0 ™J°« * » °r** to apply to it its more 

 he a, sus. Although this name is obviously incorrect, yet strictly proper designation of tarso-metatarsu . 

 in our ordinary zoological descriptions of birds, it would seem 



