662 THE LUMBAR PLEXUS. 



the cremaster muscle. In the female it accompanies the round ligament of the 

 uterus. 



(b) The crural branch (lumbo-inguinal nerve, Schmidt), descends upon the psoas 

 muscle beneath Poupart's ligament into the thigh. Immediately below that liga- 

 ment, and at the outer side of the femoral artery, it pierces the fascia lata, and 

 supplies the skin on the upper part of the thigh, communicating with the middle 

 cutaneous branch of the anterior crural nerve. Whilst it is passing beneath Pou- 

 part's ligament, some filaments are prolonged from this nerve on the femoral artery. 

 It is stated by Schmidt, that when the crural branch of the genito-crural nerve is 

 large, and commences near the plexus, he has observed it to give a muscular branch 

 to the lower border of the internal oblique and transversalis muscles. 



EXTERNAL CUTANEOUS NERVES. 



This nerve, commencing from the loop formed between the second and 

 third lumbar nerves, on emerging from the outer border of the psoas muscle, 

 crosses the iliacus muscle below the ilio-inguiual nerve, and passing beneath 

 Poupart's ligament, reaches the thigh beneath the anterior superior iliac 

 spine, where it divides into an anterior and a posterior branch distributed to 

 the integument of the outer side of the hip and thigh. 



(a) The posterior branch perforates the fascia lata, and subdivides into two or 

 three others, which turn backwards and supply the skin upon the outer surface of 

 the limb, from the upper border of the hip-bone nearly to the middle of the thigh. 

 The highest among them are crossed by the cutaneous branches from the last dorsal 

 nerve. 



(b) An anterior branch, the continuation of the nerve, is at first contained in a 

 sheath or canal formed in the substance of the fascia lata ; but, about four inches 

 below Poupart's ligament, it enters the subcutaneous fatty tissue, and is distributed 

 along the outer part of the front of the thigh, ending near the knee. The principal 

 offsets spring from its outer side. In some cases, this branch reaches quite down to 

 the knee, and communicates there with the internal saphenous nerve. 



OBTURATOR NERVE. 



The obturator nerve (internal crural) is distributed to the adductor 

 muscles of the thigh, and to the hip and knee-joints. It arises from the 

 lumbar plexus by two roots, one from the third and the other from the 

 fourth lumbar nerve. Having emerged from the inner border of the psoas 

 muscle, opposite to the brim of the pelvis, it runs along the side of the 

 pelvic cavity, above the obturator vessels, as far as the opening in the upper 

 part of the thyroid foramen, through which it escapes from the pelvis into 

 the thigh. Here it immediately divides into an anterior and a posterior 

 branch, which are separated from one another by the short adductor 

 muscle. 



A. The anterior portion communicates with the accessory obturator 

 nerve, when that nerve is present, and descends in front of the adductor 

 brevis and behind the pectineus and adductor longus muscles. It gives 

 branches as follows. 



(a) An articular branch to the hip-joint arises near the thyroid membrane. 



(b) Muscular branches are given to the gracilis and adductor longus muscles, and 

 occasionally also others to the adductor brevis and pectineus. 



(c) The terminal twig turns outwards upon the femoral artery, and surrounds that 

 vessel with small filaments. 



(d) An offset at the lower border of the adductor longus communicates beneath 

 the fascia with the internal cutaneous branch of the anterior crural nerve, and with a 

 branch of the internal saphenous nerve, forming a sort of plexus. 



Occasional cutaneous neroe. In some instances the communicating branch described 



