DISSECTION OF THE DOG 19 



on the left side of the abdomen. Not infrequently the visible part of the spleen 

 is more caudal in position and extends farther than usual towards the middle 

 line. This depends partly upon the size of the spleen, but largely upon the 

 amount of distension of the stomach. 



If the stomach is empty, possibly no part of it will be visible ; but when 

 distended a considerable extent of the sac may protrude beyond the border 

 of the liver. 



On turning the omentum over the ribs as far as possible, other organs will 

 be exposed. Coils of small intestine occupy the greater part of the field of 

 view ; but close to the pubis the urinary bladder may form a conspicuous 

 object if it happens to contain much urine. Sometimes part of the descending 

 colon can be detected ; and, if the subject be a female, part of the uterus may 

 also be exposed. It will be observed that the interior of the abdominal wall, 

 as well as the surface of the organs contained therein, is smooth and shiny. This 

 is due to the presence of a serous membrane, the peritoneum, of which the greater 

 omentum is a part. 



Intestinum tenue. — The small intestine is a long, smooth tube, measuring 

 about five times the length of the body ; and extending from the pylorus, in the 

 epigastric region — where it is continuous with the stomach — to a point slightly 

 caudal to the umbilicus and a short distance to the right of the median plane, 

 where it ends by joining the caecum. The small intestine is divided into : 

 (1) The duodenum; (2) the jejunum (intestinum jejunum), and (3). the ileum 

 (intestinum ileum). The coils of the jejunum and ileum are freely movable, 

 since they are suspended from the dorsal wall of the abdomen by a fold of 

 peritoneum, known as the mesentery (mesenterium), by way of which the blood- 

 vessels, nerves, and lymphatics gain access to the intestine. The duodenum is 

 not so mobile, as will be seen at a later stage of the dissection. To expose this 

 part of the alimentary tube, it may be necessary to turn the rest of the small 

 intestine to the left. This having been done, a portion of the duodenum will 

 be found running along the right side of the abdomen. A second part passes 

 in the opposite direction and ends at an abrupt ventral flexure not far from the 

 pylorus. A closer examination of the duodenum is better left until later. In 

 association with the duodenum one of the two limbs of the pancreas will be 

 observed. 



The terminal part of the ileum can generally be easily recognised as it 

 travels cranialwards from somewhere near the pelvic inlet to its point of 

 termination in the caecum. 



Intestinum crassum. — In calibre the large intestine of the dog does not 

 differ from the small intestine so much as it does in the other domesticated 

 mammals. In length it falls very far short of the small intestine, measuring 

 only about one-sixth of the length of the whole intestinal tube. 



For descriptive purposes, the large intestine is divided into the caecum, the 

 colon, and the rectum 



