THE HUMAN INTESTINAL CANAL. 



317 



The gullet {oesophagus) passes downward through the 

 thorax, along the vertebral column, behind the lungs and 

 the heart, and enters the ventral cavity, after penetrating 

 the diaphragm. The latter (Fig. 16, z) is a membranous, 

 muscular, transverse partition, which in all Mammals (and 

 only in these) completely separates the chest-cavity 

 (thorax, c) from the ventral cavity (c„). As has been said, 

 this division does not originally exist; at first a common 

 chest and ventral cavity, the cceloma, or the pleuro- 

 peritoneal cavity, is formed in the embryo. It is only 

 afterwards that the diaphragm forms a muscular, horizontal 

 partition between the chest and the ventral cavities. This 

 partition then completely separates the two cavities, and 

 is penetrated only by separate organs, passing through the 



FrG. 275. — Human stomach and gall-intestine in longitudinal section : 

 a, cardia (limit of the oesophagus) ; b, fundus (blind sac of the left side) ; 

 c, pylorus fold; d, pyloras valve; e, pylorus-cavity ; / a h, gall-intestine ; 

 i, mouth of the gall-duct and of the pancreas duct. (After H. Meyer.) 



chest-cavity into the ventral cavity. One of the most 

 important of these organs is the gullet (oesophagus). After 

 this has passed through the diaphragm into the ventral 

 cavity it enlarges into the stomach in which digestion 



