INTERPHALANGEAL JOINTS 311 



the bones are smaller and the joints, especially between the second and third 

 phalanges, are often ankylosed. The ligaments which unite them include, in 

 addition to the articular capsule: — 



Collateral. Dorsal. Accessory plantar. 



The two collateral ligaments are well marked, and pass on each side of the joints from a 

 little rough depression on the head of the proximal, to a rough border on the side of the base of 

 the distal phalanx of the joint. 



The dorsal ligament is thin and membranous, and extends across the joint from one col- 

 lateral ligament to the other beneath the extensor tendon, with the deep svu-face of which it is 

 connected and by which it is strengthened. 



The accessory plantar ligament covers in the joint on the plantar surface. It is a fibro- 

 cartilaginous plate, connected at the sides with the collateral ligaments, and with the bones by 

 short ligamentous fibres; the plantar surface is smooth, and grooved for the flexor tendons. 



The arteries and nerves are derived from the corresponding digital branches. 



The only movements permitted at these joints are flexion and extension. 



At the interphalangeal joint of the great toe there is very frequently a smaU sesamoid bone 

 which plays on the plantar surface of the first phalanx, in the same way as the sesamoid bones 

 of the metatarso-phalangeal joint play upon the plantar surface of the head of the metatarsal 

 bone. 



Relations of the muscles acting on the metatarso-phalangeal and interphalangeal joints 

 of the foot.— If the student wiU refer to the accounts given of the relations of the corresponding 

 joints in the hand and of the actions of the muscles upon those joints, and if he contrasts and 

 compares the muscles of the hand with those of the foot, he will readily be able to construct 

 tables of the relations of the metatarso-phalangeal and interphalangeal joints of the foot, and 

 tables of the muscles acting upon the joints. 



References. — A complete bibliography for the joints is given in the "Hand- 

 buch der Anatomic und Mechanik der Gelenke," by Professor Rudolf Fick (in von 

 Bardeleben's Handbuch der Anatomic). References are also given in the larger 

 works on human anatomy by Quain, Rauber-Kopsch, Poirier-Charpy, etc. 

 References to the most recent literature may be found in Schwalbe's Jahres- 

 bericht, the Index Medicus and the various anatomical journals. 



