Chap, xix.] THE BUTTOCK, 425 



its position is indicated by a slight but distinct depres- 

 sion over the hip. 



If a line be drawn from the anterior superior spine 

 to the most prominent part of the tuber ischii, it will 

 cross the centre of the acetabulum, and will hit the top 

 of the trochanter. This line, known as Nelaton's line, 

 is frequently made use of in the diagnosis of certain 

 injuries about the hip. For like diagnostic purposes 

 Bryant makes use of a " triangle." As the patient lies 

 in the recumbent posture, a vertical line is dropped 

 from the anterior superior spine. A second line is 

 drawn forwards from the same point to the top of the 

 great trochanter. The triangle is completed by a third 

 line joining the first two, and drawn at right angles 

 to the vertical line. A measurement of this third or 

 test line will show if any shortening has taken place 

 in the neck of the femur. It may be noted that the 

 top of the trochanter is nearly on a level with the 

 pubes. 



The tubera ischii are readily felt. They are covered 

 by the fleshy fibres of the gluteus maximus when the 

 hip is extended. But when the hip is flexed, the pro- 

 cesses become to a great extent uncovered by that 

 muscle. The muscular mass of the buttock is formed 

 by the gluteus maximus behind and by the gluteus 

 medius and minimus and tensor vaginae femoris in 

 front. The latter muscle can be seen when in action, 

 i.e., when the thigh is abducted and rotated in. 



The fold of the buttock is considerably above the 

 level of the lower border of the gluteus maximus, with 

 which it therefore does not correspond. When the 

 hip is fully extended, as in the erect posture, the but- 

 tocks are round and prominent, the gluteal fold is trans- 

 verse and very distinct. When the hip is a little flexed, 

 the buttocks become flattened, the gluteal fold be- 

 comes oblique, and to a large extent disappears. Among 

 the early symptoms of hip disease are flattening of 



