HOW ANIMALS DIGEST. 



609 



consequently we find with such food the most difficult digestion. In 

 ruminants the canal is over twenty times the length of the hody ; and 

 the stomach is divided into four chambers, to delay the food and com- 

 plete the mechanical process. The first two, however, are more prop- 

 erly expansions of the gullet. The first chamber, called the paunch 

 or rumen, stores and moistens the half-chewed food. This division in 

 the camel has a portion lined with cells for storing water. The second 

 chamber, known as the reticulum, or honey-comb stomach, receives this 

 raw material, rolls and presses it into separate balls, which are sent up 

 to the mouth for more perfect mastication. When this is complete, 

 the now semi-fluid or pasty bolus, being unable to distend the aper- 

 ture to the first and second chambers, flows into the third chamber. 

 This has its lining greatly folded in order to detain coarse materi- 

 al, whence it is called manyplies or psalterium. The fourth chamber, 



Fig. 10. The Stomach laid open behind : a, the oesophagus ; b, the cardiac dilatation ; c, the 

 lesser curvature ; d, the pylorus ; e, the biliary duct ; /, the gall-bladder ; ff, the pancreatic 

 duct, opening in common with the cystic duct opposite h ; h, i, the duodenum. 



abomasum, is the stomach proper, as here alone is the food subjected 

 to the gastric juice. 



On account of defective mastication, the whales have at least three 

 divisions of the stomach ; many mammals have two divisions ; and 

 the toothless ant-eater has a gizzard. 



Digestive Fluids. After considerable investigation, the precise 

 action of the several fluids which accomplish the chemical change of 

 food is yet unknown. Indeed, their general function is still a matter in 

 discussion. Naturally, then, our knowledge of the functions of the ac- 

 cessory digestive organs in the lower animals is limited. That diges- 

 tion, however, in all animals is the result of chemical action under the 

 influence of vital force seems assured. 



Of the several fluids or chemical agents prepared within the labora- 

 tory of the digestive apparatus, the most important and indispensable 

 vol. xvn. 39 



