138 PRACTICAL ANATOMY. 



anterior surface is ridged, convex, and presents many 

 foramina leading into the bone. The posterior surface 

 presents an oval articular surface divided into two un- 

 equal facets, the outer, large for articulation with the 

 external condyle of the femur.; the inner, smaller for 

 articulation with the inner condyle. The base presents 

 upward, and has attached to it the four-headed ex- 

 tensor muscle. The apex is bluntly pointed, and serves 

 for the attachment of the anterior ligament of the knee- 

 joint, called the ligamentum patellae. 



The patella develops by one centre; it belongs to 

 the class of irregular bones. Its cancellous tissue is 

 often arranged with the lamellae disposed transversely. 

 The outside, compact shell is dense and rather thick. 



THE TIBIA. 



Xhfi-tibia, or shin-bone, is the inner bone of the leg; it 

 belongs to the class of long bones, and presents a shaft 

 and an upper and lower extremity. The shaft is thick, 

 strong, and prismatic in form ; has three borders, an- 

 terior, inner, and outer; and three surfaces, external, 

 internal, and posterior. The anterior border is long, 

 curved, prominent, and sharp, and constitutes the "shin;" 

 it begins at the outer side of the head of the tibia, and 

 curves downward and inward, then slightly outward, 

 and, finally, by curving strongly inward, terminates at 

 the internal malleolus; for its middle three-fifths it is 

 sharp and subcutaneous. The inner border is rounded 

 and thick* it begins at the inner side of the head and 

 terminates in the internal malleolus. The outer border 

 is rather sharp, faces the inner border of the fibula, and 

 serves for the attachment of the interosseous membrane. 

 The internal surface is smooth and subcutaneous, and 

 looks forward and inward. The external surface is some- 



