POPLITEAL NERVE. 429 



with the superficial perineal nerve, and divides into an internal and an 

 external branch. t The internal branch passes down upon the inner side 

 of the testis to the scrotum ; the external branch to its outer side, and both 

 terminate in the integument of the under border of the penis. 



The Middle posterior cutaneous nerve crosses the tuberosity of the is- 

 chium and pierces the deep fascia at the lower border of the gluteus max- 

 imus. It then passes downwards along the middle of the posterior aspect 

 of the thigh and of the popliteal region, and is distributed to the integu- 

 ment as far as the middle of the calf of the leg. In its course the nerve 

 gives off several cutaneous branches to the integument of the inner and 

 outer side of the thigh, and in the popliteal region a communicating branch 

 which pierces the fascia of the leg and unites with the external saphenous 

 nerve. 



The GREAT ISCHIATIC NERVE is the largest nervous cord in the body ; 

 it is formed by the sacral plexus, or rather is a prolongation of the plexus, 

 and at its exit from the great sacro-ischiatic foramen beneath the pyriformis 

 muscle measures three quarters of an inch in breadth. It descends through 

 the middle of the space between the trochanter major and tuberosity of the 

 ischium, and along the posterior part of the thigh to about its lower third, 

 where it divides into two large terminal branches, popliteal and peroneal. 

 This division sometimes takes place at the plexus, and the two nerves 

 descend together side by side ; occasionally they are separated at their 

 commencement by a part or the whole of the pyriformis muscle. The 

 nerve in its course down the thigh rests upon the gemellus superior, ten- 

 don of the obturator internus, gemellus inferior, quadratus femoris, and 

 adductor magnus muscle, and is covered in by the gluteus maximus, 

 biceps, semi-tendinosus, and semi-membranosus. 



The Branches of the great ischiatic nerve, previously to its division, are 

 muscular and articular. The muscular branches are given off from the 

 upper part of the nerve, and supply both heads of the biceps, the semi- 

 tendinosus, semi-membranosus, and adductor magnus. The articular 

 branch descends to the upper part of the external condyle of the femur, 

 and divides into filaments which are distributed to the fibrous capsule and 

 to the synovia! membrane of the knee joint. 



The POPLITEAL NERVE passes through the middle of the popliteal space, 

 from the division of the great ischiatic nerve to the lower border of the 

 popliteus muscle, accompanies the artery beneath the arch of the soleus, 

 and becomes the posterior tibial nerve. It is superficial in the whole of 

 its coarse, and lies externally to the vein and artery. 



The Branches of the popliteal nerve are muscular or sural, and articular, 

 and a cutaneous branch, the communicans poplitei. 



The Muscular branches, of considerable. size, and four or five in num- 

 ber, are distributed to the two heads of the gastrocnemius, to the soleus, 

 plantaris, and popliteus. 



The Articular nerve pierces the ligamentum posticum Winslowii, and 

 supplies the interior of the knee joint. It usually sends a twig to the 

 popliteus muscle. 



The Communicans poplitei (communicans tibialis) is a large nerve 

 which arises from the popliteal at about the middle of its course, and de 

 scends between the two heads of the gastrocnemius, and along the groove 



