THE TARSUS: THE CALCANEUM. 



299 



Upper extremity. 



Appears about ^ 

 4th year. 



Unites about 

 25th year. 



Appears at 

 2nd. year. 



Unites about 

 20th year. 



to ossifv last : but it follows the rule which prevails with regard to the union of 

 epiphyses, by uniting first. 



Attachment of Muscles. To nine : to the head. 

 the Biceps, Soleus. and Peroneus longus ; to the 

 shaft, its anterior surface, the Extensor longus digi- 

 torum, Peroneus tertius, and Extensor proprius 

 hallticis ; to the internal surface, the Tibialis pos- 

 ticus ; to the posterior surface, the Soleus and Flexor 

 longus hallucis ; to the external surface, the Peroneus 

 longus and brevis. 



Surface Form. The only parts of the fibula which are 

 to be felt are the head and the lower part of the external sur- 

 >f the shaft and the external malleolus. The head is to 

 be seen and felt behind and to the outer side of the outer 

 tuberosity of the tibia. It presents a small, prominent 

 triangular eminence slightly above the level of the tubercle 

 of the tibia. The external malleolus presents a narrow elon- 

 gated 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. 



Surgical Anatomy. In fractures of the bones of the 

 letr both bones are usually fractured, but each 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 at the junction of the middle and lower third of 

 the bone. Many causes conduce to render this the weakest 

 part of the bone. The fracture of the fibula is usually 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 whilst 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 

 indirect 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 necrosis. Chronic 

 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 the 

 result of rarefying osteitis of a localized portion of the cancellous tissue. 



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

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

 forward and outward. 



THE FOOT (Figs. 224, 225). 



The skeleton of the Foot consists of three divisions : the Tarsus, Metatarsus, 

 and Phalanges. 



The Tarsus. 



The bones of the Tarsus are seven in number : viz. the calcaneum or os calcis, 

 astragalus, cuboid, navicular. internal, middle, and external cuneiform bones. 



Lover extremity. 



FIG. 223. Plan of the develop- 

 ment of the fibula. By three centres. 



The Calcaneum. 



The Calcaneum, or Os Calcis (<-alx. the heel), 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, 

 serving to transmit the weight of the body to the ground, and forming a strong 



