THE LOWER LIMB 



THE GLUTEAL REGION. 



Landmarks. — The crest of the ilium is almost entirely obscured by 

 the prominence of the abdominal muscles above it and the gluteus 

 medius below it, so that as a rule its position is indicated by a 

 groove. This groove conducts the finger to the posterior superior 

 iliac spine, which is on a level with the second sacral spine and the 

 centre of the sacro-iliac synchondrosis. The spinous processes of 

 the sacral vertebrae, usually four in number, may be distinguished 

 as separate projections, or they may be fused into one median ridge. 

 The fifth sacral spine being undeveloped, no median projection can 

 be felt, but at either side of the middle line the sacral comua may 

 be made out. The coccyx is felt in the natal cleft between the 

 buttocks. The tuber ischii is obscured by the lower border of the 

 gluteus maximus when the hip- joint is extended, but, when that 

 joint is flexed, the prominence is easily made out. The great 

 trochanter is felt at the lower and outer part of the gluteal region, 

 and behind it there is a natural depression. The prominence of 

 the natis or buttock is formed by the gluteus maximus, covered 

 by a large amount of adipose tissue. The fold of the natis is 

 produced by a fold of the skin and fascia, and is very perceptible 

 when the hip-joint is extended. It takes the form of a transverse 

 furrow, which commences internally a little below the lower border 

 of the gluteus maximus, and terminates externally on the surface 

 of that muscle, having crossed its lower border. The fold is hori- 

 zontal in direction, whilst the lower border of the gluteus maximus 

 is oblique. It is possible to feel the great sciatic nerve in this fold, 

 but that nerve lies deeply at a point very nearly midway between 

 the great trochanter and tuber ischii, being rather nearer the latter 

 than the former. 



Cutaneous Nerves. — ^These are met with in the following situations : 

 (i) line of origin of gluteus maximus ; (2) iliac crest ; {3) outer and 

 lower part of gluteus maximus ; and (4) lower border of gluteus 

 maximus. 



I. Line of Origin of Gluteus Maximus. — The cutaneous nerves met 

 with in this situation are divisible into three sets. 



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