THE FIBULA. 127 



versely, and projects downwards on its inner side, so as to form a thick process, the 

 internal malleolus. Inferiorly it presents for articulation with the astragalus a 

 cartilaginous surface, which is quadrilateral, concave from before backwards, and 

 having its posterior border narrower and projecting farther downwards than the 

 anterior ; internally the cartilaginous surface is continued down in a vertical 

 direction upon the internal malleolus, clothing its outer surface somewhat more 

 deeply in front than behind. The external surface is hollowed for the reception of 

 the fibula, and rough for the attachment of ligament, except over a small part along 

 the lower border. The posterior surface of the internal malleolus is marked by a 

 groove for the tendon of the tibialis posticus, and more externally is a slight 

 depression where the tendon of the flexor longus hallucis lies. 



Both tuberosities of the tibia are subcutaneous, the external forming a well- 

 marked prominence at the outer and fore part of the knee. The internal surface 

 of the shaft is thinly covered for a short distance at the upper part by the tendons 

 of the sartorius, gracilis, and semitendinosus, but in the rest of its extent it is 

 subcutaneous, together with the continuous surface of the internal malleolus. 

 Anteriorly, the tubercle gives rise to a slight elevation below the knee, on which the 

 body is supported in kneeling, and running down from this the crest is to be 

 followed, constituting the shin. 



rm- .e -L- 7 7 /length of tibia X 100\ , , , . ,, ,-, 



The femoro-tivial index ( - I is about 81 in the European, 83 in 



\ length ot femur / 



the Negro, and 86 in the Bushman. The tibia is twisted so that when the upper extremity 

 has its longest diameter directed transversely, the internal malleolus is inclined forwards : the 

 angle of torsion is commonly between 5 and 20, but it may range from to 48 (Mikulicz. 

 Arch. f. Anat., 1878). 



"Varieties. The shaft of the tibia is sometimes much compressed laterally, and expanded 

 from before back, the posterior longitudinal ridge being very prominent, so that a transverse 

 section at the junction of the upper and middle thirds has the form of a narrow lozenge : 

 such a bone is said to be platycnemlc. A facet at the anterior margin of the lower extremity 

 for articulation with the neck of the astragalus in extreme flexion of the ankle-joint is rare 

 in Europeans, but common in some lower races. (Manouvrier, " Sur le platycnemie," &c.. 

 Mem. Soc. d'Anthrop. Par., 1888 ; A. Thomson. " Influence of posture on the form of the 

 tibia," &c., Journ. Anat. xxiii and xxiv.) 



THE FIBULA. 



The fibula, or peroneal bone, is situated on the outer side of the leg ; it is nearly 

 equal to the tibia in length, but is much more slender. Its inferior extremity is 

 placed a little in advance of the superior ; and its shaft is slightly curved, so as 

 to have the convexity directed backwards, and, in the lower half, slightly inwards 

 towards the tibia. 



The superior extremity, or head, somewhat expanded, is produced upwards at 

 its hindmost part into a conical eminence, known as the styloid process ; in front of, 

 and inside this is a small oval cartilage-covered facet, looking upwards, inwards and 

 forwards, for articulation with the outer tuberosity of the tibia ; while more externally 

 is a slightly excavated surface where the tendon of the biceps femoris is inserted : 

 the outer side of the head is smooth and subcutaneous. The somewhat constricted 

 part below the head is distinguished as the neck. 



The inferior extremity, or external malleolus, is longer and more prominent 

 than the internal malleolus ; internally it forms the outer limit of the ankle joint, 

 and presents a triangular smooth surface for articulation with the astragalus, behind 

 which is a rough depression where the posterior band of the external lateral ligament 

 is attached : its anterior border, after projecting rather abruptly forwards, slopes 

 downwards and backwards : posteriorly it is marked by a shallow groove traversed 



