140 



THE VITAL PROCESSES 



rule the muscles of this coat are involuntary. They sur- 

 round the canal as thin sheets and at most places form 

 two distinct layers. In the inner layer the fibers encircle 

 the canal, but in the outer layer they run longitudinally, 

 or lengthwise, along the canal. 1 



3. An outer or serous coat, which is limited to those por- 

 tions of the canal that occupy the abdominal cavity. This 



coat is not found above the dia- 

 phragm. It is a part of the 

 lining membrane of the cavity of 

 the abdomen, called 



The Peritoneum. The peri- 

 toneum is to the abdominal cavity 

 what the pleura is to the thoracic 

 cavity. It forms the outer cover- 

 ing for the alimentary canal and 

 other abdominal organs and sup- 

 plies the inner lining of the cav- 

 ity itself. It is also the means 

 of holding these organs in place, 

 some of them being suspended 

 by it from the abdominal walls 



(Fig. 64). By the secretion of 

 FIG. 64. Diagram of the 

 peritoneum. i. Transverse a sma11 amount of liquid, it pre- 



colon. 2. Duodenum. 3. Small vents friction of the parts upon 



intestine. 4. Pancreas. one another. 



Digestive Glands. The glands which provide the dif- 

 ferent fluids for acting on -the foods derive their constitu- 

 ents from the blood. They are situated either in the 

 mucous membrane or at convenient places outside of the 



1 A layer of connective tissue between the mucous membrane and the muscular 

 coat is usually referred to as the submucovs coat. This contains numerous blood 

 vessels and nerves and binds the muscular coat to the mucous membrane. 



