THE FOO1 239 



nal malleolus presents a narrow elongated prominence, situated on a plane posterior to the 

 internal malleolus and reaching to a lower level. From it may be traced the lower third or 

 half of the external surface of the shaft of the bone in the interval between the Peroneus tertius 

 in front and the other two Peronei tendons behind. 



Applied Anatomy. In fractures of the bone* of the ley both bones are usually fractured, but 

 either bone may be broken separately, the fibula more frequently than the tibia. Fracture of 

 both bones may be caused either by direct or indirect violence. When it occurs from indirect 

 force the fracture in the tibia is usually at the junction of the middle and lower third of the bone. 

 Manv causes conduce to render this the weakest part of the bone. The fracture of the fibula 

 is usuallv at rather a higher level. These fractures present great variety, both as regards their 

 direction and condition. They may be oblique, transverse, longitudinal, or spiral. When 

 oblique, they are usually the result of indirect violence, and the direction of the fracture is from 

 behind, downward, forward, and inward in many cases, but may be downward and outward 

 or downward and backward. When transverse, the fracture is often at the upper part of the 

 bone, and is the result of direct violence. The spiral fracture usually commences as a vertical 

 fissure, involving the ankle-joint, and is associated with fracture of the fibula higher up. It is 

 the result of torsion, from twisting of the body while the foot is fixed. 



Fractures of the tibia alone are almost always the result of direct violence, except where the 

 malleolus is broken off by twists of the foot. Fractures of the fibula alone may arise from indi- 

 rect or direct force, those of the lower end being usually the result of the former, and those higher 

 up being caused by a direct blow on the part. 



The tibia and fibula, like the femur, are frequently the seat of acute osteomyelitis. Tuberculous 

 abscess is more frequently met with in the cancellous tissue of the head and lower end of the 

 tibia than in any other bone of the body. The abscess is of small size, very chronic, and prob- 

 ablv the result of tuberculous osteitis in the highly vascular growing tissue at the end of the shaft 

 near the epiphyseal cartilage in the young subject. Such an abscess in bone is called Brodie's 

 abxcess. 



The tibia is the bone which is most frequently and most extensively distorted in rhachitis. It 

 sives way at the junction of the middle and lower third, its weakest part, and presents a curve 

 forward and outward. Bow-leg is due to outward curvature of the femur, tibia, and fibula, 

 the bend being about the junction of the shafts and lower extremities. 



THE FOOT (Figs. 191, 192). 



The skeleton of the foot consists of three divisions the tarsus, metatarsus, and 

 phalanges. 



The Tarsus (ossa tarsi), The bones of the tarsus are seven in number 

 viz., the calcaneus, or os calcis, astragalus, cuboid, scaphoid, internal, middle, and 

 external cuneiform. 



The Calcaneus (os calcis} (Fig. 194). The heel bone is the largest and strongest 

 of the tarsal bones. It is irregularly cuboidal in form, having its long axis directed 

 forward and outward. It is situated at the lower and back part of the foot, 

 sen-ing to transmit the weight of the body to the ground, and forming a strong 

 lever for the muscles of the calf. It presents for examination six surfaces 

 superior, inferior, external, internal, anterior, and posterior. 



The superior surface is formed, behind, by the upper aspect of that part of the 

 os calcis which projects backward to form the heel. It varies in length in different 

 individuals; is convex from side to side, concave from before backward, and cor- 

 responds above to a mass of adipose substance placed in front of the tendo Achillis. 

 In the middle of the superior surface are two (sometimes three) articular facets, 

 separated by a broad shallow groove (sulcus calcanei), which is directed obliquely 

 forward and outward, and is rough for the attachment of the interosseous ligament 

 connecting the astragalus and os calcis. When the calcaneus is in contact with 

 the astragalus this groove is converted into a canal (sinus tarsi). Of the articular 

 surfaces, the posterior articular surface (fades articularis posterior} is the larger, and 

 is situated on the body of the bone; it is of an oblong form, wider behind than in 

 front, and convex; it articulates with the posterior facet of the astragalus. The 

 anterior articular surface is usually divided into two facets, the anterior of which 



