2(jQ OUTLINES OF EQUINE ANATOMY. 



intervertebral gaps, break up into superior and inferior 

 branches. The superior branches pass upwards to supply 

 longissimus dorsi and the other muscles in the lumbar 

 region of the back ; the inferior branches break up, sending 

 some fibres to the abdominal muscles running over trans- 

 versal! s abdominis ; others to the psoae muscles ; others 

 from the second, third, fourth, and fifth to form the crural 

 nerve, which passes along the brim of the pelvis, and 

 opposite symphysis pubis breaks up, its main portion run- 

 ning between rectus femoris and vastus internus to supply 

 the muscles clothing the front of the femur, a small, long 

 branch (saphenous nerve) passing downwards with vena 

 saphena subcutaneously as far as the hock. From the in- 

 ferior branches of the third and fourth lumbar nerves the 

 obturator nerve arises. It takes the same course as the 

 artery of the same name, and supplies the structures on 

 the external and internal surface of the obturator foramen 

 and ligament. 



The sacral nerves differ from the other spinal nerves in 

 that they run in an oblique direction outwards and back- 

 wards from their origin, thus forming that arrangement 

 in the terminal portion of the spinal or vertebral canal 

 to which the name cauda equina has been given. They 

 also divide into superior and inferior branches prior to 

 leaving the canal. The superior branches pass in an upward 

 direction through the supersacral foramina to supply the 

 anterior portion of the coccygeal muscles and the upper 

 parts of the muscles of the quarter ; the inferior branches 

 run to supply the muscles of the quarter, fibres from the 

 first sacral, and the last lumbar nerves, combining to form 

 the gluteal nerve, which passes through the foramen at 

 the anterior part of the sacro-sciatic ligament between it 

 and the ilium, thus gaining the external surface of the 

 ligament, where it supplies the muscles of the cjuarter. The 

 inferior branches of the last lumbar, with the first three 

 sacral nerves, combine to form the 



Sciatic nerve, the largest in the body, which, by passing 

 with the gluteal, gains the external surface of the sacro- 

 sciatic ligament, over which it runs on the inner surface 

 of triceps abductor femoris over the neck of the ischium, 

 between the cotyloid cavity and the tuberosity of the 

 ischium, and down as far as the superior extremity of the 

 gastrocnemii muscles. In its course behind the femur it 



