170 



EXTREMITY. 



subcutaneous; its external surface is smooth, 

 and exhibits a triangular articular facet, 

 which is united at a little more than a right 

 angle with the articular surface on the inferior 

 extremity of the tibia ; by this facet the internal 

 malleolus moves on the inner surface of the 

 body of the astragalus. The apex of the mal- 

 leolus has the internal lateral ligament of the 

 ankle-joint inserted into it ; the anterior edge 

 gives insertion to ligamentous fibres, and the 

 posterior edge, much thicker than the anterior, 

 is closely connected with the posterior surface 

 of the inferior extremity of the tibia, and has 

 upon it the oblique groove already referred to. 

 In comparing the position of the malleolus in- 

 ternus with that of the internal tuberosity of 

 the tibia, (which may best be done by laying 

 the bone on its posterior surface on a horizontal 

 plane,) it will be observed that the malleolus is 

 considerably anterior to the tuberosity, a fact 

 which is attributable to the same cause which 

 occasions the change of aspect in the inferior 

 part of each of the three surfaces of the shaft, 

 namely, a torsion of the bone similar to that 

 already noticed in the other long bones of the 

 extremities. This torsion is manifest at the 

 junction of the inferior and middle thirds, the 

 lower part having the appearance of being 

 twisted inwards, and the upper part outwards. 

 The outer side of the tarsal extremity of the 

 tibia is excavated so as to form a triangular 

 surface, rouah in its entire extent, to which the 

 fibula is applied, and into which are implanted 

 the strong ligamentous fibres by which that 

 bone is tied to the tibia. 



Structure. The cancellated texture is accu- 

 mulated in large quantity at the extremities, 

 where, especially at the superior, a line is very 

 frequently apparent on the whole circumference, 

 indicating the place of junction of the epiphysis 

 and shaft. The medullary canal is large, ap- 

 proaching the cylindrical form, and surrounded 

 by a dense compact tissue. 



Fibula (Fr. peron'e; Germ. Wadenbein). 

 This bone is situated on the outer and posterior 

 part of the tibia. It is about the same length 

 as that bone, but as its upper extremity is ap- 

 plied to the under surface of the external tube- 

 rosity, its inferior extremity projects below that 

 of the tibia. There is a slight obliquity in its 

 direction, and in consequence, its inferior extre- 

 mity advances more forwards than its superior. 



The fibula is a very slender bone in its 

 entire extent, however its extremities are a little 

 enlarged. The superior extremity or head of 

 the fibula (capitulum) is somewhat rounded on 

 its inner side, flattened on its external surface, 

 terminating superiorly in a point into which 

 the external lateral ligament of the knee-joint 

 is inserted, anterior and posterior to which the 

 edge of the bone receives the tendon of the 

 biceps muscle. At the upper and anterior 

 part of its internal surface there is a small sur- 

 face nearly plane, which is articulated with a 

 similar one on the external tuberosity of the 

 tibia. On the shaft of the fibula we may dis- 

 tingiii-ih tlm.'c surfaces, but in consequence of 

 the great extent to which the fibula appears to 

 have undergone torsion, it is at first difficult to 



detect the lines of demarcation between these 

 surfaces. The external turface is very narrow 

 and convex in its upper third, gradually ex- 

 pands as it descends, and becomes hollowed 

 out in its middle third, where it receives the 

 peronosi muscles ; in both these portions the 

 aspect of this surface is outwards and slightly 

 forwards. In the inferior third it is quite flat, 

 and its aspect is outwards and backwards. The 

 internal surface has a longitudinal sharp ridge 

 upon it, which gives insertion to the interosse- 

 ous ligament. This crest divides the internal 

 surface into two portions ; the anterior, very 

 small, in some cases not exceeding two or three 

 lines, gives attachment to the extensor muscles 

 of the toes and the peronseus tertius ; the pos- 

 terior, much more considerable and slightly 

 concave longitudinally for about its two supe- 

 rior thirds, has the tibialis posticus inserted 

 into it. This surface, which above looks nearly 

 directly inwards, looks forwards in its inferior 

 third. The posterior surface is also very nar- 

 row above, and expands as it descends ; upon 

 it the twist in the bone is very obvious. In 

 its superior third this surface looks outwards 

 and backwards ; in its middle third, where it is 

 much more expanded, it looks directly back- 

 wards; and in its inferior third its aspect is 

 inwards, and here it terminates in forming a 

 rough surface which is adapted to the similar one 

 on the fibular side of the inferior extremity of 

 the tibia. Superiorly the posterior surface of the 

 tibia gives attachment to the solceus muscle, and 

 lower down to the flexor pollicis proprius. The 

 orifice of the nutritious canal, directed down- 

 wards and forwards, is found here. 



A knowledge of the edges which separate 

 these surfaces will assist the student in 

 understanding the position of the surfaces 

 themselves. The anterior edge begins just 

 below the head, passes down in front of the 

 bone as far as the middle, then becomes exter- 

 nal and bifurcates, enclosing a triangular sur- 

 face on the outside of the inferior extremity of 

 the bone, which is quite subcutaneous. T/ie 

 external edge is at first external, and about the 

 commencement of the inferior third it begins 

 to wind round so as ultimately to become 

 posterior. The internal edge, which is the 

 most acute, and is more prominent in the centre 

 than at its extremities, passes forwards inferiorly, 

 and terminates in front of the inferior extre- 

 mity of the bone : below it gives attachment 

 to the interosseous ligament. 



The inferior extremity is long and flat, and 

 terminates in a point; it extends entirely below 

 the inferior articular surface on the tibia, and, 

 as Cruveilhier aptly remarks, it forms exter- 

 nally the pendant to the malleolus interims, 

 which it exceeds in length and thickness; it is 

 consequently called the mulleolus exli'mns. 

 The internal surface of the external malleolus 

 presents in its anterior two-thirds a plane,' 

 triangular surface for articulation with the; 

 astra^lus ; behind this surface there is an 

 excavation, which is rough, and gives insertion 

 to the posterior external lateral ligament. The 

 external surface is convex and subcutaneous, 

 and the posterior surface is grooved for the 



