268 Rev. S. Haue-hton on the Muscular Mechanism 



'& 



between the adductor magnus and flexor digitorum (fig. II.) ; 

 (d) from the tubercle of the tibia, at both sides, and from the 

 surface of the lower patella, and, by means of a fascia, to the 

 upper part of the fibula. Altogether it weighs 115^ oz. 



This enormous mass of muscles represents the gastrocnemius 

 and solfeus, intimately connected in their fleshy portion, but 

 distinct both in origin and insertion. It is inserted, as shown 

 in fig. V., by means of two powerful tendons, into the upper 

 and back part of the metatarsus, the tendon of the solseus being 

 a little above that of the gastrocnemius. 



It may be regarded as acting from the circumference of a ring 

 placed all round the knee-joint, to the tendo Achillis; and its 

 resultant pull is nearly in the axis of the leg. 



25. MM. flexores digitorum. These important muscles may, 

 in the Ostrich, be divided into two distinct groups. A. This 

 group arises from a triple origin : — (a) the condyloid pit of the 

 femur, below the origin of the gastrocnemius (fig. II.) ; (b) from 

 the outer side of the outer condyle of the femur (fig. II.) ; (c) a 

 fleshy slip connects these flexors with the belly of the digastric 

 rectus femoris in the calf of the leg. This slip is represented, 

 cut off at the point o, in fig. IV. 'Their total weight is 16 oz. 

 B. This group has a double origin : — (a) from the condyloid pit 

 of the femur ; (b) from the whole back of the fibula and tibia, 

 except the part covered by the poplitseus. Their weight is 9f oz. 



26. M. tibialis anticus. This is a flexor of the metacarpus, 

 and arises from the two anterior tubercles of the tibia and from 

 the outer side of the external condyle of the femur (fig. III.). 

 It is inserted below the heel-joint, by means of a split tendon, 

 into the front of the cannon bone, two inches below the joint 

 (fig. V.). Its weight is 8f oz. 



27. M. extensor digitorum communis (fig. V.). This muscle 

 takes a fleshy origin from the tubercles of the tibia and from 

 the crest in front of the tibia. It is inserted into the toes and 

 into the annular ligament of the phalangeal joints. It has no 

 action in flexing the cannon bone, except perhaps in some un- 

 usual position of the foot. Its weight is 5£ oz. 



28. M. poplitseus. Well marked, and rotates the fibula on 

 the tibia, f oz. 



Part II. Action of the Muscles. 



In the act of running, the leg of the Ostrich is to be regarded 

 as a jointed lever, having four joints, viz. the hip, the knee, the 

 heel, and the metatarsal joints. As the animal springs from 

 foot to foot, the whole limb, on reaching the ground, is bent as 

 far as possible at each of these articulations; and, as the spring 

 is made, the muscles proper to each joint increase the angle 



