SCIATIC AND PDDIC VESSELS. 119 



c. Muscular branches enter the gluteus maxiuiiis, the upper muscular ; 

 gemeilus, and obturator internus ; and by means of a branch to 



the quadratus, which passes with the nerve of the same name 

 beneath the gemelli and obturator internus, it gives offsets to the 

 hip-joint and the inferior gemeilus. 



d. Anastomotic branch (fig. 48). Varying in size, this artery is anasto- 

 directed outwards along the lower border of the pyriformis to the m 

 root of the great trochanter, where it anastomoses with the internal 

 circumflex and first perforating arteries. 



The INTERNAL PUDic ARTERY (fig. 48) belongs to the perineum Pudic 

 and the genital organs : it is smaller than the sciatic, internal to artery 

 which it lies. Only the small part of the vessel which winds over crosses the 

 the ischial spine is seen on the back of the pelvis, for it enters the ^ 

 perineal space through the small sacro-sciatic foramen, and is there 

 distributed. 



It supplies a small branch over the back of the sacrum, which offset*, 

 anastomoses with the gluteal and sciatic arteries ; and a twig from 

 it accompanies the nerve to the obturator internus muscle. 



The veins with the sciatic and pudic arteries receive tributaries Veins, 

 corresponding with the branches of those arteries at the back of the 

 pelvis, and open into the internal iliac vein. 



NERVES. The nerves appearing at the back of the pelvis, below Nerves come 

 the pyriformis, are derived from the plexus (sacral plexus) formed 

 within the pelvis by anterior branches from the lower two lumbar and 

 the upper four sacral nerves; the largest are furnished to parts 

 beyond the gluteal region, but some are distributed to the muscles 

 at the back of the pelvis. 



The INFERIOR GLUTEAL NERVE is larger than the superior, and inferior 

 arises from the upper part of the sacral plexus (fig. 49, i g). The 

 short trunk is directed backwards below the pyriformis, and divides 

 into numerous branches which radiate upwards and downwards, 

 and enter the gluteus maximus midway between its origin and 

 insertion. 



The SMALL SCIATIC (fig. 48) is a cutaneous nerve of the back Small 

 of the thigh. It springs from the second and third sacral nerves cutaneous* 

 (fig. 49, s s), and takes the course of the sciatic artery as far as the nerve; 

 lower border of the great gluteus, where it gives many cutaneous 

 branches. Much diminished in size at that spot, the nerve is 

 continued along the back of the thigh beneath the fascia, and 

 ends below the knee in the integuments of the back of the leg. ends in the 

 The branches distributed to, or near the buttock, are the leg ' 

 following : 



The ascending or gluteal cutaneous branches (fig. 46) turn upwards ascending 

 round the border of the gluteus maximus, and are distributed to 

 the skin over the lower third of the muscle. 



The descending cutaneous branches (fig. 46, 2 ) supply the integu- and 

 ments of the upper third of the thigh at the inner and posterior 

 aspects. One of these branches (fig. 48), which is larger than the branches ; 

 others, is distributed to the genital organs, and is named inferior inferior 

 pudendal; as it courses to the perineum, it turns below the pudendai 



