LUMBAR NERVES. 521 



The Second Lumbar, after sending off these branches, 

 passes downwards, and joins the Third lumbar nerve. From 

 this union of the second and third nerves, a branch called the 

 Cutaneous Medius, which will soon be described, proceeds 

 downwards. 



After sending off this branch, the united trunk of the second 

 and third joins the Fourth ; and from this union is sent off the 

 Obturator Nerve, which passes through the aperture in the 

 membrane that closes the foramen thyroideum ; the Crural 

 Nerve, which passes under Poupart's ligament ; and a third 

 branch that proceeds downwards, and joins the Fifth lumbar 

 nerve. The Fifth lumbar nerve, with this accession from 

 above, descends into the pelvis, and unites with the sacral 

 nerves, forming a branch called the lumbo-sacral. 



This arrangement of the lumbar nerves constitutes the 

 Lumbar Plexus, which, as has been already stated furnishes 

 three nerves to the lower extremity, namely, the Cutaneous 

 Medius, the Obturator, and the Crural Nerve. 



The Cutaneous Medius, which arises from the union of the 

 second and third nerves, and very frequently from the anterior 

 crural, as has been already observed, proceeds downwards, 

 and frequently adheres to the crural nerve, for a short distance, 

 near Poupart's ligament, but soon leaves it, and ascends on the 

 inside of the thigh, supplying the integuments as low as the knee. 



The Obturator Nerve, 



Descends into the pelvis, and passes out of it at the upper 

 part of the foramen thyroideum ; proceeding downwards in an 

 internal direction, to be distributed on the inside of the thigh. 



Its descending or saphenous branches. 10. The short saphenous nerve. 11. 

 The long or internal saphenous. 12. The obturator nerve. 13. The gluteal 

 nerve ; a branch of the lumbo-sacral nerve. 14. The internal pudic nerve. 

 15. The lesser ischiatic nerve. 16. Thl greater ischiatic nerve. 17. The pop- 

 liteal nerve. 18. The peroneal nerve. 19. The muscular branches of the pop- 

 liteal. 20. The posterior tibial nerve ; dividing at 21, into the two plantar 

 nerves. 22. The external saphenous nerve, formed by the union of the com- 

 municans poplitei and communicans peronei. 23. The anterior tibial nerve. 

 24. The musculo-cutaneous nerve, piercing the deep fascia, and dividing into 

 two cutaneous brandies, for the supply of the dorsum of the foot. 



44* 



