100 ADVANCED PHYSIOLOGY 



After the food has been in the stomach for an hour and a 

 half or two hours, the valve which has kept it from going 

 into the intestine opens and allows a little of it to pass out, 

 closing again quickly. Soon it opens again and more of the 

 digested food passes out, for this valve operates like a very 

 sensitive mechanism which allows softened, partly dissolved 

 food to pass it, but closes at once if any solid, undigested 

 food touches it. The food thus passes out of the stomach, 

 a little at a time into this long tunnel, where it is to be still 

 further dissolved and changed for absorption. Through this 

 tube the food is slowly pushed along by peristaltic action of 

 muscles in its walls, similar to those in the oesophagus. 

 Almost at once after leaving the stomach the intestine makes 

 a bend downward and to the left, thus crossing the abdomen 

 below the stomach as the duodenum; Fig. 52. As the food 

 mass is carried around this bend it is mixed with a secretion 

 which enters the intestine by a duct shown in Figure 48, and 

 which comes from two large and very important organs, the 

 liver and the pancreas. 



In many backboned animals these two organs connect with 

 the intestine through separate ducts, while in others their 

 ducts join as in man. The spleen, which is near by, has no 

 connection with the intestine physiologically. 



The Liver and its Functions. The liver is a large gland, 

 weighing in a person of average size about three pounds, 

 and located just below the diaphragm. 



It is partially divided into a number of lobes. There is a 

 large right, a smaller left lobe, and other smaller divisions, 

 which easily adjust themselves to the neighboring organs. 

 The stomach over which its lobes hang is very active; the 

 body walls are constantly moving, and the diaphragm pulls the 

 organs up and down as one breathes. To all this environment, 

 the liver adjusts itself, its lobes gliding easily over one another, 

 as well as oVer the- Organs with which they come in contact. 



Everyone is familiar wiU- the dark red appearance of the 



