OSTEOLOGY. 89 



straight ligament. Externally to this is the attachment of 

 the outer straight ligament. The posterior surface of the 

 bone is articulatory, consisting of an outer small part con- 

 nected by a broad prominent ridge with the inner large 

 part, which superiorly is concave and extends downwards, 

 inferiorly inclines forwards, terminating internally in a 

 point. The outer part plays over the outer ridge of the 

 femur, the inner over the inner ridge, the surface being 

 completed by the cartilaginous prolongation inwardly. 

 Around this surface the capsular ligament is attached ex- 

 ternally and internally. 



The TIBIA is a long round bone extending from the 

 stifle to the hock. It articulates superiorly with the femur 

 through the medium of the semilunar discs of cartilage, 

 and directly inferiorly with the astragalus; outwardly 

 with the fibula. It consists of a shaft and two extremities. 

 The shaft is prismatic presenting three surfaces, antero- 

 external, antero-internal, and posterior. The anterior sur- 

 faces centrally blend, forming a rounded margin, but 

 superiorly become expanded and unite in forming a sharp 

 ridge, which increases in size as it proceeds upwards. To 

 the internal surface of this ridge the expanded tendinous 

 layer common to ischio-tibialis, sartorius, and gracilis is 

 attached along its whole length, while biceps rotator 

 tibialis, after playing over a bursa on this sur- 

 face is attached to its prominent edge about the 

 centre. Along the sharp anterior margin externally is 

 attached the aponeurosis of triceps abductor femoris, 

 while to the external surface of the ridge, the free margin 

 of which slightly bends outwards, is attached the muscular 

 portion of flexor metatarsi. The superior extremity of the 

 ridge is triangular, bifurcating in forming two prominences 

 separated by a smooth groove. To the upper part of these 

 j)rominences the inner aud outer straight ligaments of the 

 patella are attached. While the central straight ligament, 

 after playing over a bursa situated in the groove, becomes 

 attached to the point of bifurcation. The inner prominence 

 is much the largest. The antero-internal surface is imme- 

 diately subcutaneous, and over it runs vena saphena from 

 before backwards and upwards. The anter a -external surface 

 is occupied by the passage of flexor metatarsi and extensor 

 pedis and is smooth. Inferiorly this surface^ becomes 

 wider on approaching the inferior extremity and internally 



