282 FASCIL#® AND MUSCLES OF THE HORSE 
Origin.—The transverse processes of the thoracic vertebree. 
Insertion—The lateral surfaces of the upper ends of the ribs posterior to the 
vertebral origin. 
Action.—To draw the ribs forward in inspiration. 
Structure —Arising by tendinous fibers, each muscle passes backward and out- 
ward and expands at its insertion. Some fibers pass over one rib and are inserted 
Seventh cervical vertebra-7-- 
tf a ym 
First thoracic vertebra---- 
Intercostal § 
nerves | > Levatores costarum 
= 
“.) External 
: intercostal 
Rs) muscles 
Retractor coste-— 
\  Longissimus 
costarum 
Intertransverse ligaments --7* 
Llio-lumbar ligament... 
eee Lateral border of lon- 
gissimus dorst 
--- Tuber core 
Fic. 273.—Derrpr Dissection oF DorsaL AND LUMBAR Recions oF Horse; Dorsau View. (After Schmaltz, Atlas 
d. Anat. d. Pferdes.) 
on a succeeding one. At the beginning and end of the series the muscle cannot be 
distinguished from the external intercostal, of which it is in reality only a specially 
developed part. 
Relations.—Superficially, the longissimus dorsi; deeply, the ribs, internal in- 
tercostal muscles, and the intercostal vessels and nerves. | 
Blood-supply.—Intercostal arteries. 
| 
