TENSOR VAGINiE FEMOEIS MUSCLE. 235 



all the lumbar vertebrte in the following manner : — Each slip takes 

 origin from an intervertebral disc, and from the contiguous margins of 

 the bodies of two vertebrae, the highest being attached to the neigh- 

 bouring margins of the last dorsal and first lumbar vertebrag, and the 

 lowest to the" fourth and fifth lumbar vertebrte with the intervertebral 

 substance between them. These attachments are connected by thin 

 tendinous arches extending over the middle of each vertebra, covering 

 the lumbar vessels and communicating branches of the spnpathetic 

 nerve, and giving origin to other muscular fibres. The various bundles 

 of fibres speedily unite to form a thick elongated muscle, which runs 

 along the brim of the pelvis, and emerging from the abdomen beneath 

 Poupart's ligament is inserted into the small trochanter of the femur 

 by means of a tendon, which is placed at first within the substance of 

 the muscle, and afterwards at its outer side, receiving in this manner 

 the fibres of the iliacus as well as those of the psoas. 



Relations. — Tlie psoas muscle, at its superior extremity, passes behind the dia- 

 phragm, below the arch of the ligamentum arcuatum internum. Posteriorly it is 

 in contact with the quadratus lumbormn muscle and the os innominatum. 

 Resting on its inner border along the margin of the pehas, is the external iliac 

 arteiy, and deeply in the substance of the muscle is the lumbar plexus of 

 nerves. The ilio-inguinal and external cutaneous nerves cross the Uiacus muscle, 

 and the anterior crural nei-ve descends on the tendon of the psoas. The iliac 

 fascia extends over the sm-face of the whole ilio-psoas muscle in the abdomen. 

 After emerging from the abdomen beneath Poupart's ligament, and turning 

 over the brim of the pel\-is, the tendon of the psoas rests on the capsule of the hip- 

 joint, on which it glides by means of a large sjmovial bursa, which occasionally com- 

 municates with the interior of the joint ; its outer margin is in contact with the 

 rectus muscle, and its imier margin is separated from the pectineus by the in- 

 ternal circumflex artery. 



Vu7''u'ti/. — The j^f'Oas 2Mrvi/s, an occasional muscle, placed on the surface of the 

 jisoas magnus, arises from the bodies of the last dorsal and first lumbar veitebras, 

 and from the fibro-cartilage between them, and soon ends in a flat tendon, which, 

 passes along the front and the inner side of the psoas magnus, to be inserted into 

 the ilio-pectincal line and eminence. This muscle, although it is well developed 

 and constant in animals, is most frequently absent in the human subject. It 

 was fomid in only one of twenty bodies examined by Theile with special refer- 

 ence to its existence. When present, it is liable to many changes in the place of 

 origin ; thus, it may be connected only with the first lumbar vertebra, or with 

 the second and the intervertebral substance above it, and it has been observed to 

 commence by two parts or heads separated by an iuterval. 



The tensor vaginae femoris, or ilio-aponeurotic muscle of the 

 thigh, arit^es by muscular and tendinous fibres from the external surface 

 of the iliac crest close to its fore-part, and fi-om part of the notch 

 between the two anterior iliac spines, external to the attachment of the 

 sartorius ; and passing downwards and a little outwards it is inserted 

 between two laminre of the fascia lata, from three to four inches below the 

 great trochanter of the femur. The outer of these lamiuse is continued 

 upwards on the muscle in its whole extent, being part of the general 

 investment of the limb, the deeper is connected above with the origin 

 of the rectus muscle, and Avith the fibres attaching the gluteus minimus 

 to the hip-joint. The part of the fascia, made tense by the action of 

 the muscle, forms a strong tendinous band, which descends to the outer 

 surface of the anterior tuberosity of the tibia. 



Bclatlons. — This muscle lies upon the anterior border of the gluteus minimus, 

 the upper parts of the rectus femoris and vastus extemus muscles, and the 



