416 SPECIAL ANATOMY. 



downwards and inwards, comes forth, after being more 

 deeply seated, from between m. gracilis and sartor., and 

 descends on the internal and anterior part of the leg, with 

 the ven. saphena ; it supplies the skin of the inner part 

 of the popliteal region, of the calf, of the inner malleolus 

 and back of the foot. 



6. Nervus obturatorius, arises especially from the fourth lumbar 

 nerve, passes downwards posterior and internal to m. psoas with 

 the vasa obturatoria close to the lateral parietes of the pelvis, and 

 enters the foramen in the membrana obturatoria above the artery, 

 where it divides for the supply of the mm. obluratorii [only exter- 

 nus and sends a few filaments to the hip-joint]. 



a. Ram. anterior is larger, passes forth between adductor brevis 

 and longus, supplies these, the gracilis, the skin on the internal 

 anterior region of the middle of the thigh, and, united with 

 n. cutan. fern, intern, the inner side of the calf [and knee 

 hence pains in this region in incipient disease of hip-joint], 



b. Ram. posterior perforates, and supplies the adductor longus 

 and brevis, and ramifies in the magnus as far as the knee. 



666. IV. The Sacral Nerves, Nervi sacrales, 

 (eight pairs). 



They arise (except the fifth) side by side from the inferior en- 

 largement of the spinal cord. Their roots descend, almost ver- 

 tically, in the canal, spinalis, inside of which, even, the ganglia 

 of the posterior roots are situated. The trunks of the united roots 

 are therefore longer than those of the lumbar nerves. They divide 

 soon after their exit from the sacral foramina, into their anterior 

 and posterior branches. 



a. The anterior branches decrease in thickness from the second 

 to the fifth, pass out through the foramina sacralia antt., but 

 the last between the inferior piece and the cornua of the 

 sacrum unite with n. sympathicus, and give branches to m. 

 pyriformis and coccygeus. The first to the fourth give 

 branches to the plexus in the depth of the pelvis, and form 

 the plexus ischiadicus with the fifth lumbar nerve. The fifth 

 unites with the fourth and the coccygeal nerve, and goes 

 directly into the skin of the anal region. 



b. The posterior branches are less developed, the third most. 

 They pass forth through the foram. sacral, posteriora, unite 

 with each other, with the anterior branches, and with the last 

 lumbar and coccygeal nerves, and pass as the posterior cuta- 

 neous nerves of the glutseal region ; nn. clunium poster 'iores( 3) 



