HIND-LIMB. 141 



the different segments of the limb is not so noticeable 

 as in Reptiles. The only connection of the kind which 

 may perhaps be compared with that between the flexor 

 tibialis externus and gastrocnemius of Reptiles, occurs 

 between the tendinous intersection of the caud-ilio-flexorius 

 and the inner head of the gastrocnemius. The common 

 gastrocnemius tendon (formed by the union of a tibial and 

 two femoral heads) is likewise continued over the heel to 

 the middle of the tarso-metatarsus. Certain muscles of the 

 thigh ambiens (absent in the Rook), ilio-tibialis, the two 

 portions of the caud-ilio-femoralis, and the two portions of 

 caud-ilio-flexorius are noteworthy for the approximately 

 constant variations they exhibit in different groups of birds. 

 In a similar way the particular mode of arrangement and 

 connection of the deep plantar tendons has been used for 

 taxonomic purposes. The heel is capped by a large sesamoid 

 cartilage, which, as was seen in the previous specimen of 

 the Ostrich, removes the tendons that pass over it to a 

 suitable distance from the centre of motion. 0. C. 64 Yr. 

 Presented by St. George Mivart, Esq. 



C. 186. Right hind-limb of a Rook (Trypanocorax fruyilegus), 

 showing the deep muscles. The caud-ilio-flexorius is 

 divided near its insertion into two parts by a tendinous 

 intersection. The muscle-fibres on the distal side of the 

 intersection are arranged at an angle to the long axis 

 of the proximal and larger part of the muscle, and are 

 attached to the femur close above the condyle. The ilio- 

 fibularis (biceps), before its insertion upon the fibula, 

 passes through a pulley-like tendinous loop that stretches 

 from the external femoral condyle to the origin of the 

 flexor perforates IV. By means of this mechanism the 

 power of flexing the shank upon the thigh is greatly 

 enhanced. The long flexors of the foot are very much 

 subdivided. The short extensors are reduced to a curious 

 little extensor hallucis brevis, which rises from the anterior 

 surface of the tarso-metatarsus and passes round the outer 

 surface of the first metatarsus to the dorsal surface of the 

 backwardly directed hallux. 0. C. 64 Y s. 



Presented by St. George Mivart, Es<j. 

 Shufeldt, Myology of the Raven (London, 1890), p. 155. 



