150 THE VOYAGE OF H.M.S. CHALLENGEK. 



ambiens muscle, as far as the upper border of the adductor maguus, where it termiuates by 

 dividing into the femoral and sciatic arteries. 



From the crural artery the following branches are given off. 



(1) A branch, 



Which passes off from the crural before that artery leaves the abdomen, runs backwards 

 along the external margin of the pelvic bone, and supplies the neighbouring structures. 

 From this artery a subordinate branch of small size is given off. It passes inwai'ds, and 

 accompanies the obturator nerve through the foramen ovale. 



(2) The External Circumjlex Artery 

 Is given off from the crural artery so soon as the parent trunk reaches the inner side of 

 the thigh. It passes outwards, and under cover of the sartorius divides into three or four 

 branches which supply the extensor muscles of the knee joint, including the sartorius. 

 These branches form an anastomotic chain of arteries which extends from the hip to the 

 knee joint. 



(3) Hie Femoral Artery 



Arises from the crural trunk at the upper border of the adductor magnus. It rests 

 against the adductor magnus, and extends along the inner side of the thigh as far as the 

 knee joint, where it breaks up into its terminal twigs. Differing in its mode of origin, 

 the femoral artery of the Penguins agrees with that of other birds in respect of its 

 distribution. 



(4) Tlie Sciatic Artery. 



This artery extends from the termination of the crural artery downwards to the back 

 of the knee joint. Separating from the femoral artery opposite the upper border of the 

 adductor magnus muscle, the sciatic artery passes at once from the inner to the outer 

 side of the thigh. Having gained this region, it rests upon the outer .surface of the 

 adductor magnus, as far as the knee joint, where it divides into the anterior and posterior 

 tibial arteries. As it lies along the outer side of the thigh it is concealed superficially by 

 the biceps and adductor longus muscles. 



In Spheniscus demersus the sciatic artery gives off a l)ranch which passes along the 

 back of the thigh close to the femui-. It terminates at the outer side of the knee joint, 

 by inosculating with the other branches in that region. This branch I failed to recognise 

 in any other species of Penguin. 



From the above description, it will be observed that in the Penguins the sciatic and 

 femoral arteries, instead of coming off as separate branches from the abdominal aorta, as 

 in the majority of birds, are branches of a single trunk, the crural artery, the origin of 

 which corresponds to that of the femoral in the majority of birds. This somewhat 



