266 FASCIA AND MUSCLES OF THE HORSE 



Attachments. — The small cornua close to the junction with the great cornua. 

 Action. — When relaxed, its dorsal surface is concave; when it contracts, it 

 elevates the root of the tongue. 



Structure. — Fleshy, composed of parallel transverse bundles. 

 Blood-supply. — Lingual artery. 

 Nerve-supply. — Glosso-pharyngeal nerve. 



7. Stemo-thyro-hyoideus, and 



8. Omo-hyoideus. — These are described with the muscles on the ventral sur- 

 face of the neck (p. 268). 



The Fascle and Muscles of the Neck 



It is convenient to divide the muscles of the neck (Mm. colli) into ventral and 

 lateral groups, the two lateral groups being separated from each other by the liga- 

 mentum nuchse. 



THE FASCI.E OF THE NECK 



The superficial fascia is in part two-layered, and contains the cervical cutaneous 

 muscle. The fascise of the right and left sides are attached along the dorsal line 

 of the neck to the ligamentum nuchse, while along the ventral line they meet in a 

 fibrous raphe. A deep layer is detached which passes underneath the cutaneous 

 muscle, bridges over the jugular furrow, and crosses over the deep face of the brachio- 

 cephalicus and omo-hyoideus to join the superficial layer. It again separates to 

 pass under the cervical trapezius, and become attached to the ligamentum nuchae. 

 Along the ventral line a septum is detached which separates the sterno-cephalici. 

 Two other layers in front of the shoulder enclose the prescapular lymph-glands. 



The deep fascia also forms two layers. The superficial layer is attached to 

 the wing of the atlas and the ventral edge of the longissimus capitis et atlantis and 

 scalenus. Passing downward it encloses the trachea, and, together with the deep 

 layer, furnishes sheaths for the vagus and sympathetic nerves and the carotid 

 artery. Passing upward it detaches septa between the extensor muscles of the spine. 

 Anteriorly it covers the thyroid gland, the guttural pouch, the adjacent vessels and 

 nerves, and the larynx, and is attached to the mastoid process of the temporal bone 

 and the thyroid cornu of the hyoid bone. Posteriorly it is attached to the first 

 rib and the cariniform cartilage of the sternum. The deep layer (prevertebral 

 fascia) covers the ventral surface of the longus colli, and encloses the trachea and 

 cesophagus. Anteriorly it forms, with the corresponding layer of the opposite 

 side, a septum between the guttural pouches; posteriorly it becomes continuous 

 with the endothoracic fascia. A fascia propria forms a tubular sheath around the 

 trachea, enclosing also the recurrent nerves. 



VENTRAL CERVICAL MUSCLES 



This group consists of twelve pairs of muscles which lie ventral and lateral to 

 the vertebrae. 



1. Cutaneus colli. — This has been described (p. 254). 



2. Brachiocephalicus. — This is described on p. 294. 



' 3. Stemo-cephalicus.^ — This is a long, narrow muscle which extends along the 

 ventral and lateral aspects of the trachea from the sternum to the angle of the jaw. 

 It forms the ventral boundary of the jugular furrow. 



1 This muscle is probably the homologue of the sternal part of the sterno-cleido-mastoid 

 of man. On account of the differences in its insertion in the various animals, it seems desirable 

 to adopt the name sterno-cephalicus. It is also known as the sterno-mandibularis or stemo- 

 maxillaris. 



