42G THE ANATOMY OF THE H0K8E 



the til)ift ; tlioy tuko a coui-se backwards and downwards, and ti-nninatc, 

 one on the a.stia;,'alus, tlit* other upon the lower and inner surface of tho 

 08 cnlcis. The iiitinial (hrji l!(/anieiit is an extremely thin band ; it is 

 attached alM>ve to the tibia, just below the attachment of the middle liga- 

 ment, and below to the iislra;4alus, nearly at the same point as the suiierior 

 insertion of the middle lij;ament. 



y/w aiitrrliiv /i(/it)Nriit is a thin layer, formed of decussating fibres, 

 stronger without than witliin, atladied by its superior edge to the tibia, and 

 by its inferior edges to the astragalus and to the os euneiforme parvum. 



7'hr jtontvrior li>j(tnieut, similar in structure to the anterior, is attached to 

 the wime bones, behind their articular surfaces. 



The st/uovial vicmhraue is de\eloped on the internal surface of the two 

 capsular ligaments, covered also by the three internal and the external deep 

 ligaments. 



^Movements. — This joint allows only of flexion and extension ; but to 

 Avoid contact between the foot and the tibia in the act of flexion, the tibio- 

 nstragalan articulation causes tho bones below to deviate outwards, owing 

 to the obliiiuity of the articular surfaces. 



ARTICULATIONS BETWEEN THE BONES 

 OF THE TARSUS 



The cai.canko-asthaoalan ai{ticulatio\ between tlie bones <tf the first 

 row is a compound arthrodia, resulting from the coaptatitm of three or four 

 articular surfaces on the posterior face of the astragalus to corresponding 

 faccttes on the antero inferior part of the os calcis. The lateral ligaments 

 of the tibio tarsal articulation are common to this joint; and we .also have 

 four ligaments proper to it, a superior, external, internal, and an interosseous 

 ligament. 



The siij>rrior aatvayalo-calcaiican lujanicnt, formed of very shoit and 

 parallel fibres thrown from one bone to the other, is situated near the 

 superior extremity of the trochleiw astragalan surface, and lined by the 

 .synovial membrane of the tibio-tarsal articulation. 



The lateral I'ujamcitts are two very thin bundles, which unite the os calcis 

 to the astragalus laterally, hidden under the ligaments which bind the tibia 

 to the tarsus. 



The inlerosaeoiis lUjnment is very strong, and occupies a great part of 

 the roughened excavations which separate the arthrodial surfaces of the 

 OS calcis and astragalus. These do not possess proper synovial membranes, 

 that is, membranes proper to each, with the exception of one, formed on 

 the upper and outer part of this articulation, wliere a distinct synovial 

 niembranc exists. The superior arthrodial surface is, however, .sometimes 

 Kuppliwl with synovial membrane, 1)y a prolongation from the tibio-tarsal 

 capsule. Two prolongations ascend from the capsule of this articulation 

 Ih'Iow the inferior arthrodial surf.ices of the os calcis and astragalus, and 

 thus facilitate a gliding motion, whieh is very limited. 



Tni: MOVEMENTS are so limited as to be almost null. 



In the akti(UL.\tions of the bones of the second row among them- 

 selves, the cuboid bone joins with the os scaphoides by two arthrotUal sur- 



