////; PELVIS. 283 



now continues its course in Alcock's r.inal, ,m<l through the dec]) triangular peri- 

 nea! span-, under the name of dorsal nerve of the penis, to which, with the sym- 

 pathetic from the pelvic plexus, it is distributed. 



0. I'lic small sciatic leaves the pelvis by the greater sacro-sciatic foranu-n 

 below the pyrifonnis, and breaks up into four principal cutaneous branches 



iiditig, desi ending, external, and internal. The largest of the internal branches 

 crosses the tuberosity of the ischium, and is distributed to the labia niajora under 

 tlu- name of inferior pudendal, or nerve of Soemmering. 



7. The great sciatic iicri'c takes its name at the lower border of the greater 

 sacro-sciatic foramen, through which you see it leaving the pelvis below the pyri- 

 fonnis muscle. Kxamine closely and you can see some very small branches. 

 These are articular to the hip-joint. Lower down are given off muscular branches 

 to the biceps semitenclinosus, semimembranosus, and adductor magnus muscles. 

 As a rule, the nerve divides six inches above the knee into the internal and 

 external popliteal nerves. 



Branches of the Internal Popliteal Nerve of Great Sciatic : 



1. The communicant tibialis to the communicans fibularis, a branch of the 

 external popliteal to form by this union the short saphenous. nerve. This nerve 

 supplies the skin over the superficial group of muscles of the leg. 



2. Articular brandies to the knee, with the articular arteries, superior and 

 inferior internal, and the azygos. 



V Muscular brandies to the gastrocnemius, soleus, plantaris, and popliteus. 



4. Posterior tibial, which gives off an articular branch to the ankle ; a plantar 

 cutaneous branch to the heel and sole of foot on the inner side ; muscular 

 branches to the flexor longus digitorum, tibialis posticus, flexor longus hallucis ; 

 a communicating branch to the soleus muscle. 



5. Tlic internal plantar, which gives off articular branches to the tarsus and 

 metatarsus, digital cutaneous branches to the four lesser toes, muscular branches 

 to the abductor hallucis, flexor brevis digitorum, flexor brevis hallucis, and the 

 two tibial lumbricales. 



6. External plantar, that supplies one and one-half toes cutaneously ; mus- 

 cular branches to flexor accessorius, abductor minimi digiti, the two outer lumbri- 

 cales, the adductor hallucis obliquus, the adductor hallucis transversus, the 

 flexor brevis minimi digiti, and all the interossei muscles. 



Branches of the External Popliteal of Great Sciatic : 



1. The cotniiiiinieans fibularis to the communicans tibialis to form the short 

 saphenous nerve. 



2. Three articular brandies to the knee, proceeding with the superior and 

 inferior external articular arteries and the azygos. 



3. Cutaneous (tranches to the skin covering the peronei muscles, being given 

 off with the communicans fibularis. 



4. The anterior tibial iicit'c, which gives off an articular branch to the ankle, 

 to the metatarso-phalangeal joints of all the toes. Muscular branches to the 

 tibialis anticus, extensor proprius hallucis, extensor longus digitorum, extensor 

 brevis digitorum, and a muscular branch to the first interosseous muscle. 



5. The iniisculo-ciitancons, which gives off its muscular branches to the 

 peroneus longus and peroneus brevis muscles. Cutaneous branches, internal 

 and external, to the dorsum of the foot, communicating with the internal and 

 external saphenous nerves. 



I. \\'herc is tlic lumbar plexus, located .' 



It is behind the peritoneum in the deep substance of the psoas magnus muscle. 

 :. //c,v is tlic lumbar plexus formed .' 



My the union of the anterior primary divisions of the first, second, third, and 

 a part of the fourth lumbar nerves, and the dorsi-lumbar cord. 



