THE GREAT COLON 



367 



of the base of the csecum it turns upward autl to the left behind the left sac of 

 the stomach; here it becomes constricted, and joins the small colon below the left 

 kidney. 



The caliber of the great colon varies greatly at different points. At its origin 

 it is only about two to three inches (ca. 5 to 7.5 cm.) in diameter. This soon 

 increases to about eight to ten inches (ca. 20 to 25 cm.) for the ventral portions. 

 Beyond the pelvic flexure the diameter is reduced to about three or four inches 

 (ca. 8 to 9 cm,). Near the diaphragmatic flexure the caliber rapidly increases, 

 and reaches its maximum in the last division, where it may be about twenty inches 

 (50 cm.) in its widest part. This is succeeded by a somewhat funnel-shaped 

 terminal contraction. 



— >< 



Fig. 270. — Topography of Viscera of Horse, Right Side, Deeper View. 

 i./?., First thoracic vertebra; i.L., first lumbar vertebra; ;2.A'., second sacral spine; .S', scapula; .1, humerus; 

 B, ilium; O., femur; Sch., pubis; Si., ischium; St., sternum; L., right lobe of liver; r..V., right kidney; C, 

 body, C, base, C"., apex of ctecum: r.i'.C, right ventral colon; r.Q., sternal flexure of colon; d.Q., diaphragmatic 

 flexure of colon; r.rf.C, right dorsal colon; /•'., pelvic flexure of colon; D., small intestine; H., urinary bladder; 

 M., rectum; o, left ventricle; a', right ventricle; 6, 6', right coronary artery; c, left atrium; c', right atrium; d, 

 small (left) coronary vein; e, vena azygos; /, anterior vena cava; f/, posterior vena cava; h, sinus venosus; i, 

 right phrenic nerve; k, right vagus, with its dorsal (A-') and ventral {k") divisions; I, aorta; m, oesophagus; n, 

 trachea; o, diaphragm (median section); p, right lateral ligament of liver; q, duodenum; r, dotted line indi- 

 cating position in median section of diaphragm in inspiratory phase; s, recto-coccygeus; /, suspensory ligament 

 of rectum; !/, sphincter ani; r, vesicula serainalis; w, jjrostate; i, bulbo-urethral (Cowper's) gland; y, urethra; 

 z, abdominal wall; z' , xiphoid cartilage. (After Ellenberger, in Leisering's Atlas, reduced.) 



The first part of the great colon is attached to the lesser curvature of the caecum 

 by two layers of peritoneum which form the caeco-colic fold. The ventral parts of 

 the colon are similarly connected to the dorsal parts of the same side by the meso- 

 colon. The right portions are united also by areolar tissue and muscular fibers, 

 the surface of contact being about four or five inches (ca. 10 to 12 cm.) wide; the 

 left portions are attached to each other by a peritoneal fold -wide enough to allow 

 them to be drawn apart five or six inches (ca. 12 to 15 cm.) near the pelvic flexure. 

 The terminal part of the colon is attached by peritoneum and areolar tissue to 

 the ventral surface of the pancreas dorsally and to the base of the csecum exter- 

 nally. It is connected indirectly with the diaphragm and liver by means of a fold 

 derived from the right lateral ligament of the liver. 



