SCIATIC NERVE. 525 



cutaneous ; one of these two the pudendalis longus inferior 

 (perineal cutaneous) winds round the tuberosity of the ischium 

 and is distributed to the inner surface of the scrotum, and 

 the skin on the lower surface of the penis. The other cutJme- 

 ous nerve is called the middle posterior cutaneous and is spent 

 upon the integuments of the middle and back part of the thigh 

 and of the leg as far down as the calf. On the leg it forms a 

 junction with the external saphenous nerve. 

 Some muscular branches are sent off likewise from the 

 sacral plexus to the pyriformis, gemini, and quadratus femoris 

 muscles. 



The sacral nerves unite in the sciatic plexus to form the 

 great nerve of the lower extremity, which is next to be de- 

 scribed. 



THE GREAT SCIATIC NERVE 



Proceeds from the pelvis through the ischiatic notch, between 

 the pyramidalis, and the superior gemellus muscle ; it then 

 passes down to the back part of the thigh, between the tube- 

 rosity of the ischium and the great trochanter of the os femoris ; 

 and continues downwards, inclining from within outwards, to 

 the ham, where it is situated between the tendons of the 

 semi-tendinosus and semi-membranosus on the internal side, 

 and the tendon of the biceps on the external. In this course 

 it sends off branches to the muscles on the posterior part of the 

 thigh. 



As the great nerve passes down the thigh, it sends off ob- 

 liquely downwards and outwards, a large branch which is 

 called the Fibular, that passes across the head of the fibula to 

 the external and anterior part of the leg. The place where 

 this branch separates from the main nerve is different in dif- 

 ferent subjects. It continues in contact with it for some dis- 

 tance, connected only by cellular membrane. 



The Fibular or Peroneal Nerve 



Proceeds downwards on the inside of the tendon of the 

 biceps, and crosses obliquely to the outside of the external 



