168 



OSTEOLOGY. 



Fig. 111. Plan of the Development of the Tibia. 

 By 3 Centres. 



i rt at bin, 



r ains Shaft about 

 US # y- r 



outer surface^ smooth and slightly concave, deepens the articular surface for tlie 

 astragalus. Its anterior border is rough, for the attachment of ligamentous fibres. 

 Its posterior border presents a broad and deep groove, directed obliquely down- 

 wards and inwards ; it is occasionally double, and transmits the tendons of the 

 Tibialis posticus and Flexor longus digitorum muscles. Its summit is marked by 

 a rough depression behind, for the attachment of the internal lateral ligament of 

 the ankle-joint. 



Structure. Like that of the other long bones. 



Development. By three centres (fig. Ill): one for the shaft, and one for each 

 extremity. Ossification commences in the centre of the shaft about the same time 



as in the femur, the fifth week, and 

 gradually extends towards either ex- 

 tremity. The centre for the upper 

 epiphysis appears at birth ; it is flat- 

 tened in form, and has a thin tongue- 

 shaped process in front, which forms 

 the tubercle. That for the lower 

 epiphysis appears in the second year. 

 The lower epiphysis joins the shaft 

 at about the twentieth year, and the 

 upper one about the twenty-fifth 

 year. Two additional centres occa- 

 sionally exist, one for the tongue- 

 shaped process of the upper epiphysis, 

 the tubercle, and one for the inner 

 malleolus. 



Articulations. With three bones: 

 the femur, fibula, and astragalus. 



Attachment of Muscles. To the 

 inner tuberosity, the Semi-membra- 

 nosus. To the outer tuberosity, the 

 Tibialis anticus and Extensor longus 

 digitorum. To the shaft ; its internal 

 surface, the Sartorius, Gracilis, and 

 Semi-tendinosus : to its external sur- 

 face, the Tibialis anticus : to its pos- 

 terior surface, the Popliteus, Soleus, 

 Flexor longus digitorum, and Tibialis posticus : to the tubercle, the ligamentum 

 patella?. 



THE FIBULA. 



The Fibula is situated at the outer side of the leg. It is the smaller of the 

 two bones, and, in proportion to its length, the most slender of all the long bones ; 

 it is placed nearly parallel with the tibia, its upper extremity is small, placed 

 below the level of the knee-joint, and excluded from its formation; but the 

 lower extremity inclines a little forwards, so as to be on a plane anterior to that 

 of the upper end, projects below the tibia, and forms the outer ankle. It presents 

 for examination a shaft and two extremities. 



The Upper Extremity or Head is of an irregular rounded form, presenting, 

 above, a flattened articular facet, directed upwards and inwards, for articulation 

 with a corresponding facet on the external tuberosity of the tibia. On the outer 

 side is a thick and rough prominence, continued behind into a pointed eminence, 

 the styloid process, which projects upwards from the posterior part of the head. 

 The prominence above mentioned gives attachment to the tendon of the Biceps 

 muscle, and to the long external lateral ligament of the knee, the ligament dividing 

 this tendon into two parts. The summit of the styloid process gives attachment 

 to the short external lateral ligament. The remaining part of the circumference 



Appea.rs at 2S 



Joint Shaft ai 

 2O$'i/.? 



