39 6 NERVOUS SYSTEM. 



branches, forming thus the lumbar plexus. They are also- 

 connected with the sacral plexus, so that the two are often 

 considered together as the lumbosacral plexus (Fig. 162). 

 In some other animals the first three lumbar nerves form also 

 a part of the plexus ; but they are not connected with it in the 

 cat. 



The fourth lumbar nerve forms the genitofemoral (c) and 

 part of the lateral cutaneous (d} nerves, and is connected by a 

 short strand with the fifth. The filth aids in forming the 

 lateral cutaneous (d] and femoral (_/") nerves, and is connected 

 by a short branch with the sixth. The sixth lumbar is large; 

 it forms the major part of the femoral (/") and a large part of 

 the obturator nerve (g], and sends a large connecting branch 

 caudad to join the seventh and thus pass into the sacral plexus. 

 The seventh passes caudad to join the sacral plexus and aid in 

 forming the great sciatic nerve (//) ; by its connection with the 

 sixth it aids in forming also the obturator nerve (g]. 



4. N. genitofemoralis (or N. lumboinguinalis) (c, c', c"}. 

 This is a direct continuation of the fourth lumbar nerve. Its 

 medial branch (c"} passes along the medial surface of the 

 iliopsoas (s) and the psoas minor (9) to the external iliac 

 artery, accompanies this, lying on the ventral surface, from its 

 origin to the point where it gives off the profunda femoris, then 

 accompanies the latter artery and passes onto that branch of it 

 that spreads out under the integument of the ventral pelvic 

 region. It crosses the spermatic cord and ramifies in the skin 

 of the proximal part of the medial side of the thigh. The 

 lateral branch of the genitofemoralis (c'} pierces the psoas 

 minor (9), appearing on its ventral surface opposite the fifth 

 lumbar vertebra. It passes caudad on the ventral surface of 

 this muscle, crosses the iliolumbar artery, then turns caudo- 

 laterad, passes through the abdominal wall, and is distributed 

 to the craniomedial surface of the thigh and to the adjacent 

 abdominal wall. 



This nerve is variable in origin and in distribution. Its 

 lateral branch is sometimes lacking. 



5. N. cutaneus femoris lateralis (d). The lateral cuta- 

 neous nerve arises from the connecting strand between the fourth 



