chap, xxii.) THE LEG. 501 



lower third. According to Dr. Leriche the average 

 transverse diameter of the adult tibia just below the 

 tuberosities is a little over If inches. The transverse 

 diameter at the base of the malleolus is a little less 

 than If inches, and that of the narrowest part of the 

 bone is a little more than one inch. This narrow 

 part is at the junction of the lower with the middle 

 third of the shaft and is the weakest point in the bone. 

 The relation of the compact to the cancellous 

 tissue is about the same in all parts of the shaft; but 

 according to MM. Fayel and Duret the spongy 

 tissue is arranged in two independent vertical columns, 

 one occupying the upper two-thirds and the other 

 the lower third of the bone. The minimum 

 of resistance (these authors assert) is at the point 

 where these two systems meet. Thus it happens 

 that the most common spot for a fracture of the tibia 

 is at the junction of the middle with the lower third 

 of the shaft. It is here that the bone yields when 

 broken by indirect violence, while the lesions de- 

 pending upon direct violence may be at any part of 

 the shaft. Owing to the thin covering of soft parts, 

 and the slight barrier interposed between the frac- 

 turing force and the bone, it comes to pass that 

 fractures of the leg are more often compound and 

 comminuted than are those of any other bones of the 

 extremities. If the fracture be oblique (as is commonly 

 the case when the violence is indirectly applied), the 

 line of breakage usually extends from behind, down- 

 wards, forwards and a little inwards. The lower 

 fragment, with the foot, is drawn up behind the rest 

 of the bone by the muscles of the calf, and is usually 

 displaced also outwards by the obliquity of the 

 fracture line. Often the lower fragment is slightly 

 rotated outwards by the rolling over of the foot, a 

 rotation produced by the simple weight of the limb. If 

 the fracture be transverse there may be little or no 



