THE TIBIA. 



205 



Fig. 46, 



The Tibia 



Is the long thick triangular bone, situated 

 at the internal part of the leg, and continued 

 in almost a straight line from the thigh 

 bone. The name is derived from i'ts resem- 

 blance to the ancient musical instrument. 



The upper end of the tibia is large, bul- 

 bous, and spongy. It has a horizontal sur- 

 face, divided into two cavities, by a rough, 

 irregular protuberance, which is hollow at 

 its most prominent part, as well as before and 

 behind. The anterior of the two ligaments 

 that compose the great crucial is inserted 

 into the middle cavity ; and the depression 

 behind receives the posterior ligament. The 

 two broad cavities at the sides of this pro- 

 tuberance are not equal ; for the internal is 

 oblong and deep, to receive the internal 

 condyle of the thigh bone ; while the exter- 

 nal is more superficial and round, for the 

 external condyle. In each of these two cavities of a recent 

 subject, a semilunar cartilage is placed, which is thick at its 

 convex edge, and becomes gradually thinner towards the con- 

 cave or interior edge. The thick convex edge of each cartilage 

 is connected to the capsular and other ligaments of the articu- 

 lation ; but so near to their rise from the tibia, that the cartilages 

 are not allowed to change their places; while their narrow ends 

 are fixed at the insertion of the strong cross ligament into the 

 tibia, and seem to have their substance united with it ; there- 

 fore a circular hole is left between each cartilage and the 

 ligament, in which the most prominent convex part of each 



* The tibia and fibula of the right leg, articulated and seen from the front. 

 1. The shaft of the tibia. 2. The inner tuberosity. 3. The outer tnberosity. 

 4. The spinous process. 5. The tubercle. 6. The internal or subcutaneous 

 surface of the shaft. 7. The lower extremity of the tibia. 8. The internal 

 malleolus. 9. The shaft of the fibula. 10. Its upper extremity. 11. Its lower 

 extremity, the external malleolus. 

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