242 ANATOMY OF THE HORSE. 
Action .—They seem to be for the purpose of contracting the 
dimensions of the thoracic cavity. 
5.—DORSO-COSTAL REGION. 
superficialis-costarum. — Dorso-costalis. 
Situation. —Spread over the back. 
Figure .—Broad, thin, digitated, irregular. 
Attachment .—Superiorly, to the ligamentum nuchse in its ex¬ 
tension through the back and loins : inferiorly, to the posterior 
borders, below their angles, of the 6th and all the ribs behind it. 
Relations.— Externally, with the panniculus ; anteriorly, with 
the serratus ; internally, with the transversalis costarum, and 
longissimus et spinalis dorsi; infero-posteriorly, with the obliquus 
externus abdominis. 
Structure. —Consisting of a thin aponeurosis, superiorly; from 
which originates eleven or twelve broad fleshy digitations: most 
of them (all the posterior ones) possessing thin tendinous cover¬ 
ings. The aponeurosis itself serves as a faschia to the muscles 
underneath it. 
Direction .— Downwards ; with a slight inclination forwards. 
Situation. —Upon the supero-lateral parts of the thorax. 
transversalis costarum. — Trachelo-costalis. 
Form .—Elongated ; half-penniform : broad in the middle; nar¬ 
rowing towards either extremity. 
Attachment —Posteriorly, to the anterior borders of the ribs, 
near to the spine; and to the posterior edges of their angles: an¬ 
teriorly, to the transverse process of the last cervical vertebra. 
Relations. —Externally and inferiorly, with the last muscle ; 
internally, with the costal arches; superiorly, with the longissi¬ 
mus dorsi. 
Direction. —Longitudinal: inclining downwards. 
Structure .—Complicated. Consisting of two sets of tendons : 
one set embedded in fleshy fibres, and serving to strengthen its 
attachment superiorly; the others are external, distinct from 
the other parts,-are flat and elongated, broad in the middle, grow¬ 
ing longer and more slender as they approach the extremities, 
and fixed to the costal arches. A separate tendon extends to the 
cervical vertebra in front. 
Action. —To elevate the ribs, and thus produce some enlarge¬ 
ment of the cavity of the thorax. 
levatores costarum.— Transverso-CQstales. 
Number. —About fifteen. 
Situation. —Deep-seated; upon the back. 
