276 FASCLE AND MUSCLES OF THE HORSE 
Insertion —The occipital bone, below the complexus; the tendon of insertion 
of the complexus. 
Action.—To extend the head. 
Structure—The muscle is fleshy and may be divided into two parallel parts, 
superficial and deep. The former blends somewhat with the terminal part of the 
complexus. The deep part may be termed the rectus capitis dorsalis medius. 
Bundles frequently arise from the fascia over the obliquus capitis posterior. 
Relations.—Superficially, the obliquus capitis anterior, splenius, and com- 
plexus; medially, the ligamentum nuche; deeply, the atlas, the atlanto-occipital 
articulation, and the rectus capitis dorsalis minor. The dorsal branch of the first 
cervical nerve appears between this muscle and the obliquus capitis anterior. 
Blood-supply.—Occipital artery. 
Nerve-supply.—Dorsal branch of the first cervical nerve. 
12. Rectus capitis dorsalis minor.—This small muscle lies under cover of the 
preceding. 
Origin.—The dorsal surface of the atlas. 
Insertion.—The occipital bone beneath the preceding muscle and lateral to the 
funicular part of the hgamentum nuche. 
Action.—To assist the preceding muscle. 
Structure.—It is fleshy and varies a good deal in volume, being sometimes 
small and difficult to recognize.!. On the other hand, it is sometimes double. 
Relations.—Superficially, the preceding muscle and the obliquus capitis an- 
terior; deeply, the atlas and the atlanto-occipital articulation. 
Blood-supply.—Occipital artery. 
Nerve-supply.—Dorsal branch of the first cervical nerve. 
THE FASCIZ AND MUSCLES OF THE BACK AND LOINS 
(FASCLE ET MUSCULI DORSI ET LUMBORUM) 
The superficial fascia presents no special features. The lumbo-dorsal fascia 
(Fascia lumbo-dorsalis) closely invests the muscles, but is easily stripped off the 
longissimus. It is attached medially to the supraspinous ligament and the spinous 
processes of the vertebrae; it divides laterally into two layers. The superficial 
layer is practically the aponeurosis of the latissimus dorsi. The deep layer gives 
origin to the serratus dorsalis, the lumbar part of the obliquus abdominis externus, 
the transversus abdominis, and the retractor cost. Its lateral edge curves under 
the longissimus and is attached to the ribs and lumbar transverse processes. Pos- 
teriorly it is continuous with the gluteal fascia. At the withers it forms an impor- 
tant structure, the dorso-scapular ligament. This is a strong tendinous sheet, 
attached to the third, fourth, and fifth thoracic spines. Its upper part is very 
thick and gives origin by its superficial surface to the rhomboideus thoracalis, by 
its anterior part to the splenius. The lower part is thin and elastic, and furnishes 
numerous lamelle which intersect the scapular part of the serratus ventralis and 
are attached to the scapula. Three lamellxe are detached from the ligament. 
The deepest of these passes between the longissimus and spinalis and is attached to 
the transverse processes of the first seven thoracic vertebre; it gives attachment 
to the complexus. The middle one dips in between the longissimus dorsi and 
longissimus costarum. The superficial one gives origin to the serratus dorsalis. 
A strong fascial layer, the ilio-lumbar ligament, extends from the last rib to the 
tuber coxe. 
There are nine pairs of muscles in this region, arranged in four layers. 
1 This seems due to pressure produced by pathological changes in the supra-atloid bursa, 
which are frequently extensive in dissecting-room subjects. 
