326 THE ANATOMY OF THE HORSE. 



a depression of the iliacus. It arises from the last two dorsal vertebrae 

 and the imder surfaces of the last two ribs at their upper part ; also 

 from the lumbar vertebrte except the last, covering their transverse 

 processes. It is inserted, in common with the iliacus, into the internal 

 trochanter of the femur. 



Action. — It is a flexor and an outward-rotator at the hip-joint. When 

 the hind limbs are fixed, the two muscles will arch the loins, or the single 

 muscle will incline the trunk to the same side. 



The Psoas Parvus (Plate 45). This is a smaller and more tendinous 

 muscle than the preceding, to whose inner side it is placed. It arises 

 from the bodies of the last three or four dorsal and all the lumbar 

 vertebrae. It is inserted into the ilio-pectineal eminence (of the ilium) 

 at the side of the pelvic inlet. 



Action. — To flex the pelvis on the loins when both musics act ; or to 

 incline it laterally when a single muscle acts. If the pelvis be fixed, it 

 will execute the same movements on the loins. 



Directions. — Eaise the outer edge of the psoas magnus, and remove it 

 except its fibres of origin beneath the rim of the diaphragm and its 

 conical tendon of insertion, as in Plate 45. 



The Iliacus (Plates 45 and 16). This is a powerful fleshy muscle 

 which, when the psoas magnus muscle is in position, appears to consist 

 of an outer and an inner portion. In reality, however, it is a single 

 mass, with a deep groove in it for the terminal tendon of the psoas 

 magnus. It arises from the entire iliac surface of the ilium, from its 

 external angle, and from the sacro-iliao ligament. It is inserted into the 

 inner trochanter of the femur, in common with the psoas magnus. 



Action. — The same as the psoas magnus. 



The QuADRATUS Lumboeum (Plate 45). This muscle lies under cover 

 of the great psoas muscle. Its most external and strongest fasciculus 

 arises from the sacro-iliac ligament. It is inserted by this same fasciculus 

 into the tips of the lumbar transverse processes, and into the hinder 

 edge of the last rib. From the main fasciculus others pass inwards to 

 the lumbar transverse processes, and to the under surfaces of the three 

 last ribs, close to the spine. 



Action. — To assist in bending the loins to the side of the acting muscle. 

 Both muscles, by fixing the last ribs, will enable the diaphragm to act 

 to more advantage. 



Lumbar Intertransverse Muscles (Plate 45). These are thin 

 muscular and tendinous strata connecting the edges of adjacent lumbar 

 transverse processes. 



Action. — To assist in bending the loins to the side on which the 

 muscles act. 



Directions. — An examination of the diaphragm will complete the 

 dissection of the abdomen. Define its pillars attaching it to the lumbar 



