62 ANTHROPOLOGY. 



lunar form, and in the median line ; one for the inferior vena cava {foramen 

 vence cavce or quadr Hater um\ nearly square, and to the right side ; and one 

 for the oesophagus {hiatus cesophageus), elliptical, and to the left side. 



The quadratus lumborum is a thick, flat, irregularly square muscle, 

 situated in the lumbar region next the spine, forming part of the posterior 

 wall of the abdomen. It arises from the posterior fourth of the crest of the 

 ilium and from the ilio-lumbar ligament ; it is inserted into the extremity 

 of the transverse processes of the four first lumbar vertebrae and of the 

 last dorsal. Its use is to bend the spine to one side, to depress the last 

 rib, and thus assist in expiration ; both muscles acting together support the 

 spine. 



Psoas parvus, a long, thin, and narrow muscle, is situated behind the 

 psoas magnus and arises from the lower edge of the side of the body of the 

 last dorsal vertebra, also from the body of the first lumbar, and the inter- 

 vertebral substance; it ends in a thin tendon which crosses the psoas 

 magnus and is inserted into the ilio-pectineal eminence and adjacent part 

 of the brim of the pelvis. Use : to assist in bending forwards the body or 

 in raising the pelvis. 



Psoas magnus extends along the sides of the lumbar vertebrse, the brim 

 of the pelvis, and the anterior and inner part of the thigh, as a long, round, 

 and fleshy muscle. It arises by two planes of fasciculi, the one anterior 

 from the sides of the border of the two last dorsal and four first lumbar 

 vertebrse ; the other posterior, from the bases of the transverse processes. 

 The fibres become attached to a tendon in common with those of the 

 iliacus muscle, which passing around the hip joint becomes inserted into 

 and around the lesser trochanter of the femur. Its use is to flex the thigh 

 on the pelvis, or the pelvis on the thigh ; in standing it supports the 

 spine and prevents its bending backwards; it is especially concerned in 

 walking. 



The iliacus interims, a flat, radiated, or triangular muscle, arises from the 

 transverse process of the last lumbar vertebra, ilio-lumbar ligament, base 

 of the sacrum, inner margin of the crest of the ilium, the brim of the ace- 

 tabulum, &c., and is inserted into the common tendon of the psoas magnus 

 as already described. It assists the psoas in flexing and rotating the 

 thigh. 



We next proceed to the consideration of the perinseal muscles, the first 

 of which is the sphincter ani externus, a flat, thin, oval muscle, open in the 

 middle. It arises from a fibro-cellular substance extending from the os 

 coccygis to the rectum (recto-coccygeal ligament), and encircling the anal 

 orifice, is inserted into the raphe or prominent hard ridge of the perinseum 

 and into the superficial fascia. It serves to close and raise the anus, also 

 to draw the bulb of the urethra downwards and backwards, and to com- 

 press it. 



The sphincter ani internus vel orbicularis is a thick fasciculus of mus- 

 cular fibres, encircling the lower extremity of the rectum, with no attach- 

 ment to the rectum behind, and only a slight one to the central point 

 before, but is in close contact with the mucous membrane of the intestine. 

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