REPORT ON THE SPHENISCID^. 163 



prove acceptable to some, would probably be objected to by other anatomists. The 

 facts being stated, such views may be based upon them as may occur to different 

 morphologists. 



Thus defined the lumbo-sacral nerves are thirteen in number. 



The anterior division of the first lumbo-sacral nerve, in respect of its distribution, 

 closely resembles the last dorsal nerve. It extends downwards, parallel to the anterior 

 division of the last dorsal nerve, and breaks up into branches which supply the muscles 

 and skin of the anterior abdominal wall. This nerve has no connection with either the 

 last dorsal or the second lumbar nerve in any species except Eudyptes chrysocome from 

 Tristan, and hence takes no share in the formation of the crural plexus. 



The second lumbo-sacral nerve gives off a branch which passes downwards, parallel 

 to the first lumbo-sacral nerve, which it closely resembles in its course and distribution. 

 It is distributed to the muscles of the abdominal wall. Having given off this branch, the 

 second lumbar nerve unites with the anterior division of the third and a portion of the 

 fourth lumbar nerve to form the crural plexus. 



The Crural Plexus. 



The crural plexus (fig. 2) is formed by the union of a portion of the second with the 

 whole of the third and one-half of the fourth of the anterior divisions of the lumbo- 

 sacral nerves. These nerves unite to form a plexiform arrangement, from which two 

 large nerves — the crural and obturator — are derived. 



Tlie Crural Nerve. 



The crural nerve (1) ^ is formed by the union of branches from the second, third, and 

 fourth lumbar nerves. It passes from the pelvic cavity in company with the crural artery 

 and vein, and, having reached the inner side of the thigh, at once breaks up into a 

 number of branches, which are distributed as follows: — 



(a) A branch (2) enters the posterior border of the sartorius and supplies that muscle. 



(6) Three branches (3, 4, and 5) are given off close together from the crural nerve, 



immediately after the latter has escaped from the pelvic cavity. They pass to the rectus 



femoris, gluteus medius, and gluteus minimus respectively, and enter the deeper surfaces 



of these muscles. The branch to the rectus femoris also supplies the tensor fasciae 



femoris. 



(c) Three or four twigs derived from the crural nerve (6) are distributed to the 

 extensor cruris muscle, and along with these two branches pass off for the supply of the 

 gracilis (7) and amhiens (8) muscles. 



{d) The crural nerve also supplies a branch to the pectineus. 



(e) A large cutaneous nerve (9), derived from the crural trunk, in addition to the 



' The figures in brackets refer to tlie annexed diagram of the crural and sciatic plexus. 



