1896.] ANATOMY OF PETROGALB XANTHOPUS. 691 



fabella articulates with the head of the fibula. The internal 

 lateral ligament extends down the inner side of the head of the 

 tibia for about an inch below tlie level of the joint ; its anterior 

 fibres are attached highest and its posterior lowest. The two 

 crucial ligaments are strong and have the usual attachments. The 

 external semilunar cartilage is attached anteriorly to the tibia just 

 behind the anterior crucial ; posteriorly it turns up to be attached 

 to the posterior part of the external surface of the internal condyle 

 some way behind the attachment of the posterior crucial ligament. 

 Externally the popliteus tendon is connected to the convex margin 

 of the cartilage. Besides the above-named posterior attachment 

 of the external semilunar cartilage there is a nai-row baud wliich 

 binds it feebly to the posterior margin of the head of the tibia. 

 The synovial membrane of the joint is continued upward under 

 the quadriceps tendon for about half an inch above the top of 

 the articular cartilage of the trochlea. The ligamentum muco- 

 sum is well marked and contains a pad of fat in its lower part ; 

 above it is continued up as a uarrow tube of synovial membrane 

 to the posterior margin of the trochlea. The internal semilunar 

 cartilage is attached anteriorly nearly opposite the external, 

 posteriorly it is fixed to the tibia in front of the posterior crucial 

 ligament. 



Fig. 5. 



A.C E.S 



Lower end of femur of Pctroffale, with ligaments attached. 

 (Same lettering as fig. 4.) 



The Tihio-Jibular Articulations. — The lower half of the fibula has 

 a concave surface where it is in contact with the tibia and is bouud 

 to that bone by fairly strong interosseous ligaments. The upper 

 half of the fibula allows the head to glide backward and forward on 

 the external tuberosity of the tibia for about | inch. During 

 internal rotation of the leg on the thigh the head of the fibula is 

 pressed back by the external condyle of the femur and forms a 

 spring-like bufier to check that movement. The superior tibio- 



