424 DIGESTIVE SYSTEM OF THE HORSE 
to the first part of the colon by the ceeco-colic fold. The apex is free, and conse- 
quently may vary in position. 
The czecum has four longitudinal bands (T:enize cxci), situated on the dorsal, 
ventral, right, and left surfaces; these cause four rows of sacculations (Haustra). 
The ventral band is almost entirely exposed or free (Tienia libera); it begins on the highest 
part of the base, extends along the medial side of the greater curvature, and joins the medial band 
near the apex. It is concealed only at its origin where the bowel is attached to the wall. The 
dorsal band extends along the lesser curvature from the termination of the ileum to the apex. 
The medial band extends along the medial part of the lesser curvature of the base, inclines 
ventrally further forward, and ends by joining the ventral band. It is covered at its origin by the 
adhesion to the right dorsal part of the great colon and beyond this by the cecal vessels and lymph 
glands. Medial to the termination of the ileum it projects from the wall of the bowel as a faleiform 
band which can be felt distinctly although covered by vessels and fat. The lateral band is 
continuous with that of the right ventral part of the colon. It is covered by vessels, lymph glands 
and fat, but can be felt in its posterior part, where it forms a concave projecting edge. It inclines 
ventrally in front and may extend to the apex or fade out without reaching it. 
Fig. 363.—Ortrices or Cacum or Horse. 
1, Ileo-cxcal orifice; 2, cxeco-colic orifice; 3, intervening fold. 
The ileo-cecal orifice (Ostium ileocecale) is situated in the lesser curvature of 
the base, about two or three inches (ca. 5 to 7.5 em.) to the right of the median 
plane, and in a transverse plane through the first or second lumbar vertebra. The 
end of the ileum is partially telescoped into the caecum, so that the orifice is sur- 
rounded by a fold of mucous membrane which encloses a thick circular muscular 
layer, the sphincter ilei. 
The caeco-colic orifice (Ostium cxecocolicum) is lateral to the preceding one; 
the interval between them is only about two inches (ca. 5 em.), and they are separ- 
ated by a large fold which projects into the interior of the cecum. The orifice is 
small in relation to the size of the ezecum and colon. — It is slit-like, or has a narrow 
oval outline, and is about two inches (ca. 5 em.) long. It has a thick valvular fold 
(Valvula czecocolica) at its ventral margin and is encircled by a muscular ring, the 
sphincter ceci.t Large crescentic or semilunar folds (Plicze exci) project into the 
cavity of the bowel, and between these are large pouches (Cellule czci). 
1 The anatomical arrangement gives no support to the view which is sometimes expressed 
that ingesta may pass directly from the ileum to the colon. 
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