430 DIGESTIVE SYSTEM OF THE HORSE 
flexure of the great colon; ventrally to the bladder (when full) or to the uterus. 
The second part of the rectum is related dorsally and laterally to the pelvic wall. 
Ventrally the relations differ in the two sexes. In the male they are the bladder, 
the terminal parts of the ductus deferentes, the vesiculze seminales, the prostate, 
the bulbo-urethral glands and the urethra. In the female they are the uterus, 
vagina, and vulva.! 
STRUCTURE OF THE LARGE INTESTINE 
The serous coat covers the different parts in varying degree. It does not 
cover (a) the opposed surfaces of the cecum and colon which are between the layers 
Fic. 369.—TopoacrapHy oF VisceRA OF Mare; Lerr Deep View. 
1R., First thoracic vertebra; 1L., first lumbar vertebra; 2K., second sacral spine; S., scapula; A., humerus; 
B., ilium; F., femur; Sch., pubis; S?z., ischium; L., liver (left lobe); Ma., stomach, the posterior contour of which is 
indicated by dotted line x; Mi., spleen; l.N., left kidney, concealed part indicated by dotted line; M., small colon; D., 
small intestine, parts of which have been removed; J.d.C., left dorsal colon; l.v.C., left ventral colon; v.Q., sternal 
flexure; d.Q., diaphragmatic flexure; O., left ovary; U., horn of uterus; L.l., broad ligament of uterus; M’., rectum; V., 
vagina; H., bladder; a, left ventricle; a’, right ventricle; b, left coronary artery with descending (b’) and circumflex 
(b”) branches; ec, left auricle; d, pulmonary artery (cut); e, aorta; f, ligamentum arteriosum; g, brachiocephalic trunk 
(anterior aorta); h, trachea; 7, esophagus; fk, left phrenic nerve; J, diaphragm in median section; m, uterine tube; 
n, bursa ovar o, urethra; p, cut edge of broad ligament; gq, line of reflection of pelvic peritoneum; r, recto-coceygeus; 
s, suspensory ligament of rectum; ¢, sphincter ani internus; u, sacro-coccygeus ventralis; 1, abdominal wall in section; 
w, xiphoid cartilage. (After Ellenberger, in Leisering's Atlas.) 
of the cxeo-colic fold and mesocolon; (b) the areas of parietal attacament of the 
excum and colon; (c) the retroperitoneal part of the rectum. 
The muscular coat consists of longitudinal and circular fibers. The bulk of | — 
the former is in the bands of the cecum and colon. It is to be noted, however, 
that the bands of the cecum and the ventral parts of the great colon are largely | — 
composed of elastic tissue. The bands of the dorsal parts of the colon are largely 
muscular, and those of the small colon are almost entirely muscular. Some of the 
circular fibers pass from one part of the colon to another, where they are attached 
to each other, forming the fibre transverse coli. The muscular coat of the ampulla 
of the rectum presents special features. The longitudinal layer of fibers is very 
1 The anterior part of the rectum is variable in position and relations. 'The amount covered | 
| 
by peritoneum dorsally and laterally is very variable, and appears to be in inverse proportion to 
the fulness of the bowel. 
ANATOMY 
