156 



THE ARTICULATIONS. 



pairs, extend to the summits of the sesamoids. That which is sent to each external 

 sesamoid gives off, on the side of the first phalanx, a reinforcing band to the proper 

 Win- Q extensor of the digit. The two last, profound and median, descend 



into the interarticular notch of the metacarpal bone, after becoming 

 a single fasciculus , afterwards, they pass between the two internal 

 metacarpo-phalangeal ligaments, and separate from each other in 

 passing downwards and forwards on the inner side of the first 

 phalanx, to join the proper extensor tendon of each digit. 



In the Pig, Dog, and Cat, for each metacarpo-phalangeal there 

 is : a proper synovial membrane ; an intersesamoid ligament ; an 

 inferior sesamoid ligament composed of two cross-bands ; two small 

 lateral sesamoid ligaments; two lateral metacarpo-phalangeal liga- 

 ments, attached interiorly to the first phalanx and the sesamoids ; 

 an anterior capsular ligament, in the centre of which is found a 

 small bony nucleus, a kind of anterior sesamoid, over which glides 

 one of the branches of the common extensor of the digits. The 

 suspensory ligament is replaced by real palmar interosseous muscles 

 (see the Muscles of the fore-foot). Some fibres situated between the 

 first phalanges of the great digits in the Pig, remind one of the 

 superior interdigital ligament of the Ox. 



In Man, the cavity in the upper extremity of the first phalanx 

 is completed by a glenoid ligament. The glenoid ligaments of the 

 four first digits are united to each other by a transverse ligament 

 of the metacarpus. The articulations are consolidated by two 

 lateral ligaments. The metacarpo-phalangeal articulations allow 

 flexion and extension movements, us well as those of abduction 

 and adduction ; but the latter are limited by the lateral ligaments. 



7. Articulation of the First with tlie Second Plwilanx, or 

 First Interpnalangeal Articulation. 



(Preparation. Kemove the extensor tendon; throw open the 

 metacarpo-phalangeal sheath, and turn down the flexor tendons.) 



This is an imperfect hinge-joint. 



Articular surfaces. On the inferior extremity of the 

 first phalanx, there, are two lateral condyles separated by a 

 groove. On the superior surface of the second phalanx, there 

 are two glenoid cavities and an antero- posterior ridge. 



The latter surface is completed behind by a glenoidal 

 fibro-cartilage, very dense and thick, which also acts as 

 a ligament. It is attached, in one direction, to the 

 second phalanx, between the superior articular surface 

 and the kind of fixed sesamoid which margins it behind ; 

 PHALANGEAL AND in the other, it is inserted into the first phalanx by means 

 INTER - PHALAN- of six fibrous bands : two superior, which embrace the 

 inferior, middle, and superficial sesamoid ligaments ; two 

 r middle and two inferior, which extend to the sides of the 



. inferior extremity of the first phalanx. This fibro-car- 

 1, o, Outer and inner -, -i -i / , , ,1 , -i /. / ,1 



rudimentary me- tilage is moulded, in front, to the articular surface of the 



tatarsal bones ; 2, latter bone, and forms, by its posterior face, a gliding 

 Perforans tendon 



and its check ligament ; 4, Suspensory ligament ; 5, Gliding surface, or sheath far the 

 flexor tendons, formed by the posterior face of the sesamoid bones, and intersesamoid, 

 transverse, and annular ligaments ; 6, Section of lateral sesamoid ligament ; 7, Lateral 

 fasciculus of the middle 'inferior sesamoid ligament ; 8, Inferior superficial sesamoid 

 ligament ; 9, Lateral ligament of the first interphalangeal articulation ; 10, Section 

 of the terminal branch of the perforatus tendon; 11, Section of the lateral cartilage 

 of the foot; 12, Postero-inferior surface of navicular bone; 13, Section of lateral car- 

 tilage, plantar cushion, and wing of pedal bone ; 14, Perforatus tendon ; 15, Perforans 

 tendon. 



F 



THti MKl ACAK.1 U- 



GEAL ARTICULA- 

 TIONS J 

 LIMB. 



