198 SHUFELDT. 



bone. The shaft, likewise, exhibits a curvature from one extremity to 

 the other, the greatest amount being at its middle; the entire convexity 

 is on the outer side. The shaft of the tibia in most mammals is triangular 

 in section, but in Cynocephalus it is quite quadrilateral, especially where 

 its caliber is at its minimum. A shallow longitudinal groove marks its 

 outer aspect, being best seen along the middle third ; otherwise the bone, 

 or I'ather its continuity, is devoid of any particular characters. 



The proximal end, or what is known as the head of the bone, is expanded 

 and nearly as big as the distal end of the femur. This expansion gives 

 rise to two lateral eminences, the tuberosities of the tibia. They support 

 siiperiorly the twti smooth concavities with which the condyles of the 

 femur articulate in life. In extent they are of about equal size, and 

 between them toward the back of the bone is a low, pointed process, the 

 spinous process of the tibia. A slight notch occurs in the posterior border 

 bounding the tibial head which has received the name of the popliteal 

 notch, and to it the posterior crucial ligament is attached. On the oiiter 

 side of the head there occurs a flat, subeircular, articular facet intended 

 for the head of the fibula. It is of no great size. Posteriorly, the 

 boundary of the head somewhat overhangs or extends beyond the shaft, 

 which is here broad, flat, and smooth. 



The enlarged distal end of the tibia is not more than one-half the 

 bulk of the proximal extremity, and it has a form to fulfill a variety of 

 purposes. Chief among these are its articulation with one of the bones 

 of the metacarpus, its articulation with the fibula, for the passage of 

 tendons of certain muscles, and for ligamentous attacliment. At its 

 inner side it is prolonged distally into a prominent process which is the 

 internal malleohis. Just above this there is a deep, oblique groove, its 

 lower opening being in front. In life this groove gives passage to the 

 tendons of the fiexer longus digitorum and the tibialis posticus muscles. 

 There is a small, rough, inconspicuous facet on the outer side of this distal 

 end of the bone with which the lower end of the fibula articulates. The 

 extreme inierior surface of this extremity is given over entirely to a 

 broad, spindle-shaped, articulate concavity which in life articulates with 

 the astragalus ; internally this is carried slightly up the shaft, or at least 

 upon the back of this end of the bone. In front this extremity is 

 convex from side to side and very smooth ; over it in life glide the extensor 

 tendons. 



The fibula is very nearly as long as the tibia, being exceeded only by 

 the internal malleolus of the latter. On the whole it is the most slender 

 long-bone in the skeleton and, for its length, the straightest. Some 

 sj^ecimens have the proximal moiety reduced to extreme slendemess 

 while the head of the bone at that end, which makes a feeble articulation 

 with the tibia, is always reduced to a mere semiellipsoidal nib, only a 

 few millimeters long, flattened on its inner articular aspect, and convex 



