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ANATOMY OF THE HORSE. 
muscles and quadratus lumborum ; infero-posteriorly, with the 
kidneys, renal capsules, pancreas and duodenum; on the right 
side, with the liver; on the left, with the stomach and spleen. 
Direction .—-The fibres of the larger muscle all converge in 
radii, and run to the condiform tendon as to a common centre : 
those of the appendices run longitudinally. 
Structure .—It is made up of fleshy and tendinous parts. 
The fleshy parts are those forming the circumferent portions of 
the large muscle, and the principal bulk of the crura or appen¬ 
dices. The tendinous parts consist in a thin circular expansion 
occupying the middle of the larger muscle, and uniting that with 
the lesser. Through the muscle are to be seen three remarkable 
openings: a superior one, in the interspace between the crura, 
for the aorta; one, a little lower, formed by the decussation of 
the crura for the oesophagus; and a third, or lower one, perforat- 
ng the cordiform tendon, for the vena cava posterior. 
Action .—The diaphragm is the principal if not the sole agent 
in inspiration: it acts in opposition to the abdominal muscles, 
which are the chief expiratory powers. By the contraction of its 
radiated fibres, aided by that of the crura, the cordiform tendon 
is transformed to a plane surface, and the dimensions of the 
chest from before backwards thereby considerably augmented. 
Its capacity, however, is again contracted in consequence of the 
muscle resuming its concavo-convex form, from the reaction of 
the abdominal muscles and consequent pressure against it of the 
abdominal viscera. There are occasions, however, in which these 
opponent respiratory agents co-operate to one and the same effect: 
such is the case in the expulsion of urinary and faecal matters; 
and also in the act of parturition. 
MUSCLES OF THE ABDOMEN. 
LUMBAR REGION. 
The muscles included within this region constitute the fleshy 
parts of the loins. They are six pairs in number, altogether; 
and two of them are placed externally; the other four, internally. 
SEMI-SPINALIS LUMBORUM. 
Consisting of regular layers of fleshy fibres, similarly distri¬ 
buted in the loins to what those of the semi-spinalis dorsi are in 
the back; and continued along the sacrum. They are covered 
by thin tendinous faschiae extended from transverse to spinous 
process. 
