OF THE SOUTHERN APTERYX. 293 



into the anterior part of the tendon of the broad rectus, and into tlie anterior and inner 

 part of the head of the tibia. Its insertion is partly covered by the internal head of the 

 gastrocnemius. 



It bends and adducts the thigh, and extends the leg. 



The homologue of the Biceps flexor cruris (PI. XXXI. XXXII. k) is a unicipital mus- 

 cle, corresponding with the rectm extensor in the characteristic modification of its ex- 

 tended origin, in relation to the great antero-posterior development of the pelvic bones : 

 it is exposed by the removal of the rectus. Orig. By a broad and thin aponeurotic ten- 

 don, which at first is confluent with that of the rectus but soon becomes distinct, from the 

 posterior prolongation of the ilium : there is no second head from the femur. Ins. The 

 fleshy fibres converge as they descend along the back and outer part of the thigh, and 

 finally terminate in a strong round tendon, which glides through a loop (x) formed, as 

 m the common Fowl, Ostrich, &c., by a ligament extended from the back of the outer 

 condyle of the femur to the head of the tibia, and is inserted into the process on the out- 

 side of the fibula one inch from its proximal extremity. By means of the loop the weight 

 of the hinder parts of the body is partially transferred, when the leg is bent, to the 

 distal end of the femur; and the biceps is enabled, by the same beautiful and simple 

 mechanism, to efi-ect a more rapid and extensive inflection of the leg than it otherwise 

 could have produced by the simple contraction of its fibres. 



Semimembranosus (PI. XXXII. XXXV. l).— Origin. From the side of the coccygeal 

 vertebra, and from the posterior end of the ischium ; it crosses the superficial or internal 

 side of the semitendinosus. Ins. Into the fascia covering the gastrocnemius and the inside 

 of the tibia : through the medium of Ihe fascia it acts upon the tendon (a*) of the in- 

 ternal gastrocnemius. 



Semitendinosus (PI. XXXII. XXXV. M).-This muscle arises from the posterior and 

 outer part of the sacrum and the aponeurosis connecting it with the ischium : it is a flat- 

 tened triangular muscle, which receives the square accessorius muscle (n) from the lower 

 and posterior part of the femur. It gradually diminishes as it descends, and having passed 

 the knee-joint, sends oft' at right angles a broad and square sheet of aponeurosis, which 

 glides between the two origins of the gastrocnemius internus, and is inserted into the 

 lower part of the angular ridge continued from the inside of the head of the tibia. The 

 terminal tendon, continued from the apex of the muscle, then runs along the outer or 

 fibular margin of the internal head of the gastrocnemius, and becomes confluent with the 

 tendon of that muscle at r* Pi. XXXV. 



Crurceus (PI. XXXII. XXXV. o).-This is a simple but strong muscle .- it commences 

 at the upper and anterior part of the thigh by two extremities, of which the outer and 

 upper one, representing the vastus externus, has its origin extended to the base of the 

 trochanter ; the inner and inferior comes ofl^- from the inner side of the femur, beneath the 

 insertion of the gluteus magnus ; the two portions blend into one muscle much eariier than 

 in the Ostrich. Ins. By the ligamentum patellte into the fore-part of the head of the tibia. 



VOL. III. PART IV. 2 R 



