590 A MANUAL OF ANATOMY 



and it receives the deep expansions of the digital processes of the 

 central division of the plantar fascia. It is to be noted that the 

 transverse metatarsal ligament includes the head of the first 

 metatarsal bone, whereas the corresponding ligament in the hand 

 (transverse metacarpal) excludes the head of the first metacarpal 

 bone. 



Summary of the Tarsal and Tarso- metatarsal Synovial Membranes. 

 — These are usually six in number. 



1. Posterior astragalo-calcaneal. 



2. Astragalo-calcaneo-navicular. 



3. Calcaneo-cuboid. 



4. Naviculo-cuneiform, cubo-cuneiform, cubo-navicular (incon- 

 stant), intercuneiform, and middle tarso-metatarsal. 



5. Internal tarso-metatarsal. 



6. External tarso-metatarsal or cubo-metatarsal. 



Sometimes the middle tarso-metatarsal synovial membrane is 

 distinct from the naviculo-cuneiform and intercuneiform synovial 

 membrane, in which case the number would be increased to seven. 

 Occasionally the cubo-cuneiform synovial membrane is distinct 

 from the naviculo-cuneiform and intercuneiform, in which case 

 there would be eight synovial membranes. In addition to these, 

 there may be a synovial bursa between the contiguous sides of the 

 bases of the first and second metatarsals if these articulate with 

 each other, as they sometimes do. 



The Metatarso-phalangeal Joints. 



These joints belong to the class diarthrosis, and to the subdivision 

 condylarthrosis or condyloid joint. They are formed by the heads 

 of the metatarsal bones and the proximal ends of the first 

 phalanges. The ligaments of the four outer joints are three in 

 number, two lateral and an inferior or plantar fibrous plate. In the 

 metatarso-phalangeal joint of the great toe the plantar fibrous 

 plate of the other joints is replaced by two sesamoid bones, which 

 are closely associated with the ■ heads of insertion of the flexor 

 brevis hallucis. In the case of each joint the expansion of an 

 extensor tendon serves the purpose of a dorsal ligament. Each 

 joint is provided with a synovial membrane. The ligaments, 

 synovial membranes, and movements of these joints closely 

 correspond with those of the metacarpo-phalangeal joints. Abduc- 

 tion, adduction, and circumduction, however, are much more 

 limited. 



Arterial Supply. — ^The plantar digital and dorsal interosseous 

 arteries. 



Nerve-supply. — ^The deej) division of the external plantar nerve 

 (either directly or through its branches to the interosseous muscles), 

 or the adjacent digital nerves. 



