no 



OSTEOLOGY. 



Fig. 112. Plan of the Development of 

 the Fibula. By 3 Centres. 



j. 7 ? abou 



Its upper three-fourths are divided into an anterior and a posterior portion by a 

 very prominent ridge already mentioned, the oblique line of the fibula. The 

 anterior portion is directed inwards, and is grooved for the attachment of the 

 Tibialis posticus muscle. The posterior portion is continuous below with the 

 rough triangular surface above the articular facet of the outer malleolus ; it is 

 directed backwards above, backwards and inwards at its middle, directly inwards 

 below. Its upper fourth is rough, for the attachment of the Soleus muscle : its 

 lower part presents a triangular rough surface, connected to the tibia by a strong 

 interosseous ligament, and between these two points the entire surface is covered 

 by the fibres of origin of the Flexor longus pollicis muscle. At about the middle 

 of this surface is the nutritious foramen, which is directed downwards. 



In order to distinguish the side to which the bone belongs, hold it with the 



lower extremity downwards, and the broad 

 groove for the Peronei tendons backwards, to- 

 wards the holder, the triangular subcutaneous 

 surface will then be directed to the side to which 

 the bone belongs. 



Articulations. With two bones: the tibia and 

 astragalus. 



Development. By three centres (fig. 112): 

 one for the shaft, and one for each extremity. 

 Ossification commences in the shaft about the 

 sixth week of foetal life, a little later than in 

 the tibia, and extends gradually towards the 

 extremities. At birth both ends are cartilaginous. 

 Ossification commences in the lower end in the 

 second year, and in the upper one about the 

 fourth year. The lower epiphysis, the first in 

 which ossification commences, becomes united 

 to the shaft about the twentieth year, con- 

 trary to the law which appears to prevail with 

 regard to the junction of the epiphysis with the 

 shaft ; the upper one is joined about the twenty- 

 fifth year. 



Attachment of Muscles. To the head; the 

 Biceps, Soleus, and Peroneus longus. To the 

 shaft, its anterior surface ; the Extensor longus 

 digitorum, Peroneus tertius, and Extensor lon- 

 gus pollicis : to the internal surface ; the Soleus, 

 Tibialis posticus, and Flexor longus pollicis : to 

 the external surface ; the Peroneus longus and brevis. 



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THE FOOT. 



The Foot (figs. 113 and 114) is the terminal part of the inferior extremity ; it 

 serves to support the body in the erect posture, and is an important instrument of 

 locomotion. It 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, scaphoid, internal, middle, and external cuneiform bones. 



THE CALCANEUM. 



The Calcaneum or Os Calcis is the largest and strongest of the tarsal bones. 

 It is irregularly cuboidal in form, and situated at the lower and back part of the 



