110 



DISSECTION OF THE BUTTOCK. 



seek cuta- 

 neous nerves 

 on the crest 



and by side 

 of sacrum : 



other nerves 

 of small 

 sciatic 

 below : 



cutaneous 

 arteries. 



Sources of 

 the cutane- 

 ous nerves : 



from last 

 dorsal ; 



from lumbar 

 plexus, 



through 

 ilio-hypo- 

 gastric, and 



external 

 cutaneous : 



from pos- 

 terior 

 branches of 



lumbar 



and sacral 

 nerves ; 



below the great trochanter (H). The flap of skin thus marked out 

 is to be thrown forwards. 



Many of the cutaneous nerves of this region will be found in the 

 fat along the line of the iliac crest (fig. 46). Thus, in front, but 

 rather below the crest, are branches of the external cutaneous. 

 Crossing the crest towards the fore part is a large offset of the last 

 dorsal nerve ; and usually farther back, but close to the bone, a 

 smaller branch from the ilio-hypogastric nerve. At the outer 

 border of the erector spinee are two or three branches of the 

 lumbar nerves. 



By the side of the sacrum and coccyx two or three offsets of the 

 sacral nerves are to be looked for beneath the fat. 



The remaining cutaneous nerves are derived from the small 

 sciatic, and must be sought beneath the fat along the line of the 

 lower incision, where they come from underneath the glutens 

 maximus. Some turn upwards over that muscle, and others ar< 

 directed down the thigh. 



Cutaneous arteries accompany all the nerves, and will serve as 

 guides to their situation. 



CUTANEOUS NERVES (fig. 46, also fig. 2, p. 4). The nerves 

 distributed in the integuments of the buttock are small but 

 numerous, and are derived from the last dorsal nerve, from 

 branches of the lumbar and sacral plexuses, and from the posterior 

 primary divisions of the lumbar and sacral nerves. 



The LAST DORSAL NERVE (fig. 46) ( 8 ) supplies the buttock by 

 means of its lateral cutaneous branch. This offset perforates the 

 muscles of the abdomen, and crosses the front of the iliac crest 

 to be distributed over the fore part of the gluteal region, as low as 

 the great trochanter. 



NERVES OF THE LUMBAR PLEXUS. Parts of two nerves of the 

 plexus of the lumbar nerves, viz., ilio-hypogastric from the first, 

 and the external cutaneous from the second and third, are spent in 

 the integuments of this region. 



The iliac branch of the ilio-hypogastric ( 7 ) crosses the iliac crest in 

 front of the lumbar nerves, lying in a groove in the bone, and 

 extends generally only a short distance below the crest. 



Offsets of the posterior branch of the external cutaneous nerve of 

 the thigh bend back wards to the integuments above the great 

 trochanter, and cross the ramifications of the last dorsal nerve 

 (see fig. 2, p. 4). 



POSTERIOR PRIMARY BRANCHES. The offsets of the posterior 

 primary pieces of the lumbar nerves ( 6 ) are two or three in number, 

 and cross the crest of the ilium at the outer edge of the erector 

 spinae ; they ramify in the integuments of the middle of the buttock, 

 and some branches may be traced nearly to the great trochanter. 



The branches of the sacral nerves ( 5 ) perforate the glutens maxi- 

 mus near the sacrum and coccyx, and are then directed outwards 

 for a short distance in the integuments over the muscle. These 

 offsets are usually two in number : the largest is opposite the lower 

 end of the sacrum, and the other by the side of the coccyx. 



