THE INTESTINAL CANAL. 



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branes a serous, muscular, fibrous, and mucous membrane. 

 It is divided into the large and small intestines. The 

 smaller intestine is composed of the duodenum, jejunum, 

 and ileum. The duodenum is so named because it measures 



Fig. 23. Transverse section of the thoracic and abdominal cavities. 



A. Heart 



B. Lungs separated to show the heart. 



C. Diaphragm. 



D. Liver. 



E. Gall-bladder. 



F. Stomach. 



G. Small intestine. 

 H. Transverse colon. 



nearly twelve finger-breadths in length; it extends from the 

 stomach to the jejunum, from which no line of demarcation 

 separates it, nor is the jejunum separated from the ileum. 

 These names indicate a purely arbitrary distinction, drawn 

 by the ancient anatomists between these three parts of the 

 intestinal canal. The large intestine differs from the small 

 one externally in size, and because it presents a series of more 



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