MUSCULAR SYSTEM. 119 



it grows thin and less expansive, and, aboutopposite to the withers, 

 altogether vanishes. The fleshy part (which in its course adheres 

 closely to the articulations of the vertebrae with the ribs) is pretty 

 uniform in its breadth until it arrives at the withers, opposite to 

 where it divides into three tails or portions, of a flattened pyra- 

 midal form, and so disposed that one, more or less, overlaps 

 another. Of these, the inferior division is the direct continuation 

 of the common fleshy belly : from it proceed six or seven flat ten- 

 dons, which goto be fixed to the ribs at their articulations with the 

 transverse processes. The middle division sends oft" three broad 

 thin tendons, to be fixed to the three last transverse processes of 

 the neck. The superior division is a small conical slip, ending 

 in a slender tendon, which is attached to the same process of the 

 fourth cervical vertebra. These tendons are all embedded in, and 

 intermediately connected by, continuous fleshy parts, which adhere 

 to the costal articulations at the withers, and to the oblique pro- 

 cesses and sides of the bodies of the three posteriormost vertebrae 

 of the neck. 



Action. — It will incline to a state of flexion the fore quarters 

 upon the hind; or the hind upon the fore ; according as the one 

 or the other are made the fixed points. It is a principal agent in 

 the acts of kicking, and rearing, and leaping. If one act by 

 itself, the fore or hind parts of the body will be inclined to one 

 side. The pair will also assist in the erection of the neck. 



SPINALIS DORSI. 



Situation. — Deep-seated upon the withers. 



Form. — Thick, elongated, pyramidal: base turned down- 

 wards. 



Attachment. — Posteriorly, through the medium of the aponeuro- 

 sis of the longissimus dorsi, to the spinous processes of several of the 

 posterior dorsal vertebrae : anteriorly, to the spines of the six or 

 seven anterior dorsal vertebrae, and to those of the three or four 

 posterior cervical. 



Relations. — Externally and superiorly, with the trapezius, be- 

 hind, andcomplexus major, in front ; internally,with the ligament- 

 um nuchae ; and, inferiorly, it is inseparably united with the last 

 muscle. 



Direction. — Longitudinal. 



Structure. — Thebroad and thick part is covered by a broad patch 

 of inseparably adherent aponeurosis, which grows thin and less ap- 

 parent posteriorly ; but, anteriorly, ends in a broad tendon, which 

 pierces the fleshy termination of the belly, and becomes fixed to 

 the spine of the last cervical vertebra. 



