50 THE VOYAGE OF H.M.S. CHALLENGER. 



The crucial ligaments of the knee joint are two in number. The anterior is attached 

 below to the anterior horn of the single semilunar cartilage, and above to the intercondy- 

 loid depression of the lower end of the femur. The posterior crucial ligament is 

 continuous below with the posterior horn of the semilunar cartilage, and above, it, like 

 the anterior crucial ligament, is inserted into the intercondyloid femoral notch. 



The ankle joint is surrounded by a strong capsular ligament, which is attached to the 

 contiguous extremities of the Iwnes which enter into its formation. Posteriorly and 

 laterally this capsule is strengthened by special ligaments. Posteriorly a stout 

 quadrilateral plate of fibro-cartdage is attached below to the posterior border of the 

 upper extremity of the tarso-metarsal bone, while above it presents a free border. This 

 plate is perforated for the transmission of the tendons of the long flexor muscles of the 

 toes. The capsule of the joint is farther strengthened by lateral ligaments, which, how- 

 ever, are not so well defined as are the corresponding structures of the knee joint. 



In the interior of the ankle joint there is a single semilunar cartilage which intervenes 

 between the upper extremity of the outer metatarsal bone and the external of the two 

 lower tibial condyles. This cartilage moves freely on both bones, and is continuous in 

 front with the anterior crucial ligament, and behind with the fibro-cartihxginous plate 

 which completes the joint posteriorly. 



The crucial ligaments are two in number. Both are attached above to the inter- 

 condyloid notch on the lower end of the tibia. The anterior or external is inserted below 

 into the base of the outer metatarsal bone, while the posterior or internal is inserted 

 into the anterior border of the upper end of the tarso-metatarsal bone. Both of these 

 ligaments are drawn tense when the foot is extended upon the tibia. 



The metatarso-phalangeal joints are each provided with a capsular ligament, which is 

 strengthened laterally and superiorly by special ligamentous bands. The plantar surface 

 of each is defended by a plate of fibro-cartilage, over which glide the tendons of the 

 long flexor muscles of the toes. 



The intei-phalangeal articulations are similarly arranged, except that superior 

 ligamentous bands are absent. 



The metatarsal bone of the hallux is attached to that of the second toe by a few 

 ligamentous fibres. The separate elements of the hallux are connected together by 

 delicate capsular ligaments. 



III.— MYOLOGY. 

 (Plates VIIL, IX., X.) 



The muscidar anatomy of one or other species of the Spheniscid^ has been previously 

 described, either in whole or in part, by Schoepss, Reid, Gervais and Alix, and isolated 

 references to the myology of the group occur in the standard works of such writers upon 



