182 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



ligament. Between the two sides of the duodenal loop stretches the mesoduo- 

 denum, a portion of the mesentery of the intestine. In this is situated the pan- 

 creas, lying between the two limbs of the loop. From a deep depression in the 

 dorsal surface of the right lobe of the liver, the two bile ducts (there is no gall 

 bladder) emerge and pass into the duodenum. The left bile duct is the shorter 

 and stouter of the two and enters the left limb of the duodenum about half an 

 inch beyond the gizzard. The more slender right bile duct passes to the right 

 limb of the duodenal loop. There are three pancreatic ducts, all of which pass 

 from the right side of the pancreas into the right limb of the duodenal loop. One 

 of these arises from the anterior part of the pancreas and passes obliquely forward, 

 entering the duodenum near the anterior termination of the right limb of the 

 loop. The other two ducts emerge from the middle of the pancreas and pass 

 across to the right limb of the duodenum. The ducts are generally easily seen 

 by spreading out the mesentery. 



Trace the small intestine posteriorly from the duodenum. It is much coiled 

 and supported by the mesentery , which, owing to the small space into which the 

 intestine is packed, is fused in many places. Near its termination the small 

 intestine turns toward the median line, widens slightly, and then runs straight 

 caudad in the median line. At about the middle of the peritoneal cavity it 

 passes without enlargement into the large intestine. The point of junction of 

 large and small intestine is marked by a pair of small lateral diverticula, the 

 caeca. The large intestine is so short as to constitute little more than a rectum 

 which soon passes into the cloaca. Owing to the absence of pubic and ischial 

 symphyses in birds, the cloaca in birds does not pass through the ring of the 

 pelvic girdle but may be traced directly to the anus. There is no urinary blad- 

 der. In female specimens the single left oviduct will probably be noted entering 

 the left side of the cloaca. The single ovary (left one) is situated in the anterior 

 part of the peritoneal cavity, dorsal to the gizzard. 



Make a drawing of the digestive tract. 



The gizzard and proventriculus may now be freed from the adjacent air sacs 

 and the mesenteries. On turning the gizzard far forward there will be found 

 between the proventriculus and the anterior end of the right limb of the duodenal 

 loop a rounded red body, the spleen. The gizzard may now be cut open along 

 its posterior margin. The interior contains small stones and probably partially 

 digested food. Note the extremely thick muscular walls and the hard horny 

 lining of the gizzard. Cut from the gizzard into the proventriculus and note the 

 soft glandular walls of the latter. The gizzard grinds up the food into small 

 pieces, thus taking the place of teeth, and the proventriculus digests the food by 

 means of the digestive fluid secreted by the glands in its walls. 



6. The pleural cavities and their contents.— The posterior intermediate air 

 sac situated in the oblique septum may now be punctured if this has not already 

 been done. The two walls of the septum are now more clearly observable. The 



