ARTICULATIONS OF THE LOWER EXTREMITIES. 305 



of them is called anterior, and the other posterior, from their re- 

 lative situations to each othcc. The first arises from the inter- 

 nal face of the external eondyle, by a depression near the bot- 

 tom of the notch and just at the margin of the articular surface ; 

 it descends forwards, and is inserted immediately in front of 

 the little ridge between the articular fac.es of the tibia-. The 

 second arises from the bottom of the notch between the condyles, 

 just behind the trochlea for the patella, upon a surface that may 

 be considered as belonging to the internal eondyle; it descends 

 backward-s :md is inserted into the rough surface behind the 

 aforesaid spine or ridge of the Libia. The crucial ligaments arc- 

 large, round, and composed of parallel fibres very closely com- 

 pacted; their strength is very considerable, and they servo not 

 only to limit the extension of the leg, but also to cheek any 

 ^ like rotation inwards. 



The Semilunar Cartilages (Cartllagines Scmilunares, fal- 

 are two in number; one placed on either side of the su- 

 perior face of the tibia, hoi ween it and the condyles of the os 

 femoris. Their .shape is su.Ticiently indicated by their names, 

 and as they are placed on the circumference of each articular 

 surface of the tibia, leaving the middle uncovered, they increase 

 considerably the depth of the concavities for receiving the con- 

 dyles. Their external circumference is thick, whereas, the in- 

 ternal is reduced by a gradual diminution of their thickness, to 

 a very thin edge. The internal cartilage is but little more than 

 a semicircle, and is longer in its antero-posterior diameter than 

 in its transverse: on the other hand, the external is almost cir- 

 cular; an arrangement by which each is suited to its rcspectirc 

 surface. They adhere by their greater circumferences to the 

 fibrous matter surrounding the joint, particularly the lateral li- 

 gaments, but not so closely as to prevent their sliding back- 

 wards and forwards in the flexions of the leg. The tendon of 

 the popliteus adheres to the external, either directly or by the 

 intervention of a small synovial sac. 



The internal semiluriar cartilage is attached by its fore ex- 

 tremity to the anterior internal side o"!" the roughne ;s in front of 

 the ridge, called spinous process, on the top of the tibia, and by 

 the hind extremity to the posterior face of the base of the ridge, 

 just in advance of the posterior crucial ligament. The external 

 cartilage is attache 1 by its anterior end, also, to the roughru 



20* 



