846 



A MANUAL OF ANATOMY 



branch, and is known as the nervus bigeminus. The anterior 

 primary division of the fourth sacral nerve also divides into an 

 upper and a lower branch, and it is known as a nervus furcalis. 

 The lumbo-sacral cord in two divisions, ventral and dorsal, the 

 anterior primary divisions of the first two sacral nerves, the upper 

 and lower branches of the third sacral, and the small upper branch 

 of the fourth sacral form the sacral plexus, whilst the large lower 

 branch of the fourth sacral, the fifth sacral, and the coccygeal form 

 the sacro-coccygeal plexus. 



Sacral Plexus. — ^This plexus, formed as stated, is a large flattened 



To Lumbar Plexus 



CREAT "" 

 SCIATIC 



Pudic 



Fig. 366.— a, The Sacral Plexus 

 A 



1, I, I. Nerve to Quadratus Femoris 



2, 2, 2. Nerve to Obturator Internus 



3, 3, 3. Small Sciatic Nerve 



Perforating Cutaneous 



To Coccygeal Plexus 



B, The Sacro-Coccygeal Plexds. 

 B 



4.S. Fourth Sacral, giving a Branch to 

 Sacral Plexus 

 V. Visceral Branches 

 M. Muscular Branches 

 T.C. Terminal Cutaneous Branches 



mass, lying upon the pyriformis muscle, and behind the parietal 

 pelvic fascia, which separates it from the sciatic and pudic vessels. 

 The mass ultimately forms two bands, upper and lower. The 

 upper or sciatic band, which is the larger of the two, receives the 

 lumbo-sacral cord, first sacral, larger portion of the second sacral, 

 and upper branch of the third sacral nerves. It is fiat and somewhat 

 triangular, and is continued into the great sciatic nerve, which 

 leaves the pelvis through the lower part of the great sacro-sciatic 



