POSTERIOR PART OF LOWER EXTREMITY. 



Dissection. Locate greater trochantcr, sacrum, coccyx, tuber of iscliitim, 

 crest of ilium, inner and outer hamstrings, head of fibula, neck of fibula, os calcis, 

 inner and outer malleoli. 



Incisions. (i) From centre of crest of ilium to centre of the os calcis ; (2) 

 from greater trochanter to coccyx ; (3) from internal to external condyle ; 

 141 from inner malleolus to outer malleolus. Cut deeply enough to permit the 

 ,i-s of the skin to separate one-half of an inch with ease. In removing the 

 skin from any area, cut closely enough that light may shine through the skin. 

 The thing you see now having removed the skin is the superficial fascia. It 

 contains the following structures in a variable amount of fat (Fig. 255) : 



Cnttinei>its or sensory nerves in figure 255. 



1. The twelfth or last thoracic nerve below the twelfth rib. 



2. The iliac branch of the ilio-Jiypogastric nerve. 



3. Posterior brandies of the lumbar and sacral nerves. 



4. The external cutaneous nerve of the lumbar plexus. 



5. The small sciatic of the sacral plexus. 



6. The cutaneous branch of the obturator nerve. 



7. Tangs from the long or internal saphtnous, 



8. The short sap/tenons, formed, as you see in figure 255, by the communicans 

 tibialis and communicans fibularis, branches of internal and external popliteal 

 respectively. 



9. The short sap/tenons rein, with the nerve described in the preceding para- 

 graph. This vein comes from the outer end of the dorsal arch of the foot, runs 

 behind the outer malleolus of the fibula, passes up the mid-line of the leg, 

 between the two heads of the gastrocnemius muscle, pierces the deep popliteal 

 fascia, and opens into the popliteal vein. 



Describe the twelfth thoracic nerve. 



It is seen giving (i) a cutaneous branch to the anterior part of the gluteal 

 region ; (2) a cutaneous branch to the anterior part of the abdominal walls as low 

 .is the hypogastric region. The nerve lies below the last rib, with the first lumbar 

 artery. It crosses the quadratus lumborum muscle, and its muscular branches 

 are distributed like the other abdominal intercostals. 



Jfcscribc the ilio-hypogastric nerve. 



This is a branch of the lumbar plexus, being given off from the first lumbar 

 with the ilio-ingninal nerve. The iliac branch supplies the integument of the 

 front part of the gluteal region. The hypogastric branch pierces the aponeurosis 

 of the external oblique muscle one inch above the external abdominal ring, and 

 supplies the skin in this region. 



Observe that the posterior branches of the lumbar and sacral nerves supply 

 tin- skin over the gluteus maximus muscle. 



Remember, the external cutaneous branch of the lumbar plexus supplies the 

 skin covering the vastus externus, and mav be considered a dismembered branch 



o ' . - 



of the .interior crural nerve, according to Hilton's law. 



365 



