360 , William Mackenzie : 



A not infrequent condition is a, separation of the shaft into 

 two portions at the junction of the middle and lower thirds. 

 Though unassociated with disability in walking j-et in some 

 cases the ends may form prominences beneath the skin for which 

 the surgeon may be consulted. That there is a lack of resis- 

 tance of the narrow lower third of the leg is undeniable, affect- 

 ing not only the bony structures but the soft also, since Rickets 

 here first manifests itself, and ulcers of the leg are usually met 

 with at this spot. 



Associated with the narrowing of the lower third of the leg 

 which is necessary for activity of movement, since size and 

 weight would impede locomotion, we have practically no origin 

 of muscular fibi-es ; the muscles are becoming more or less 

 tendinous ; they lie close to the bones and are held firmly 

 in position by strong bands of fascia. 



It will now be necessary to enter on a desci'iption of the 

 Fibula as it occurs in animals of different specit^s, the animals 

 chosen having undoubtedly an important bearing on the com- 

 parison. 



Koala ( Phascolar,tus chiereus). 



In both the Koala and the Australian Phalanger with the 

 hind foot broad and an opposable and serviceable Hallux there 

 exists a greater freedom of movement between the Tibia and 

 Fibula than in others of the marsupialia, approaching in some 

 degree to the rotation between the Radius and Ulna. In Koala 

 the disproportion between the Tibia and Fibula is slight and 

 excepting the monitor lizard (Varanus) less than that occurring 

 in the other forms examined. The head of the bone is well 

 developed and articulates with the Sesamoid bone in the outer 

 head of the Gastroenemius with the outer tuberosity of the 

 Tibia and also with the outer condyle of the Femur, so that 

 it partakes in the knee-joint. The lower end is well developed, 

 with the outer Malleolus slight, and the Fibula is seen to play 

 as almost an important part in the formation of the ankle- 

 joint as the Tibia. 



Lemur [Leiiun- catta). 



Here as in the case of the Koala there is a wide range of 

 movement at the ankle-joint and the Fibula is well developed 



