164 



THE VOYAGE OF H.M.S. CHALLENGER. 



branches above mentioned, comes off from the crural nerve so soon as it has reached 

 the inner side of the thigh. It passes downwards, and coming into relation with the 

 terminal portion of the femoral artery, opposite the inner side of the knee joint, is 

 distributed to the skin of the inner side of the leg as low as the ankle joint. This branch 

 closely resembles the saphenous nerve of the mammal. 



(/") A second cwto?ieo?(s branch (10), derived from the crural trunk, winds forwards in 

 front of the extensor cruris muscle, to reach the outer side of the thigh, where it becomes 

 cutaneous by passing between the sartorius and extensor cruris muscles. Having reached 

 the skin, this branch divides into two parts, both of which extend downwards as far as 



D 



ILS- 

 2 



Fig. 2. — Diagram showing the distribution of the Lumbo-Sacral and Coccygeal Nerves oi Eudyptes chrysocome 



from Kerguelen. 



the calf of the leg, supplying in their course branches to the skin covering the outer side 

 of the thigh and the outer head of the gastrocnemius. 



The Obturator Nerve. 



The obturator nerve (11) is formed by the union of branches from the third and 

 fourth lumbar nerves. It passes obliquely backwards, and escapes from the pelvis along 

 with the tendon of the obturator internus muscle, by passing through the foramen ovale. 

 Before leaving the pelvic cavity, the obturator nerve gives a branch to the obturator 

 internus (12), and, having reached the thigh, it supplies the adductor magnus (13) and 

 the obturator externus (14) muscles. 



