332 



BACKBONED ANIMALS, 



food or cud is chewed twice before it is finally digested.* 

 The molar teeth have two double, crescent-shaped folds, 

 and, in biting, the incisors of the lower jaw are pressed 



Bet. 



FIG. 356. Stomach of a ruminant (sheep) : a?, oesophagus ; Ru, paunch ; 

 ret, honey-comb ; Ps, manyplies ; a, true digestive stomach or rennet ; 

 du, beginning of intestine. 



against the opposite and toothless gum of the upper. The 

 stomach (Fig. 356), with few exceptions, is divided into 

 four compartments : i. The paunch, ru ; 2. The honey- 



*.The grass, partly chewed and mixed with saliva, is swallowed, 

 and passes into the oesophagus ; the latter is continued into a tube 

 with a long slit on its under side, whose lips fit closely, and are 

 water-tight. The tube thus formed leads naturally to the third stom- 

 ach, and here ve sec a wonderful provision. The coarse food as it is 

 swallowed at first, from its size presses open the slit, and drops into 

 stomach No. I, or paunch, where it is mixed with water. From here it 

 goes into stomach No. 2, or the honeycomb, where the polygonal spaces 

 may serve to fashion it into pellets or cuds. Now, by a simultaneous 

 contraction of the diaphragm and abdominal muscles, a cud is forced 

 against the cardiac aperture of the stomach into the oesophagus, and so 

 into the mouth, where it is chewed by the molar teeth, and again swal- 

 lowed at last ready for digestion. As it passes down for the second 

 time, we would perhaps expect it to press open the slit and drop into 

 the first stomach again ; the second chewing, however, has reduced it 

 to a pulp, so that it is now not large enough, and it passes along the 

 tube over the slit and into the third stomach or manyplies, where it 

 is strained ; then passing into the true stomach, where it is mixed with 

 the gastric juice and absorbed. 



