

DIGESTIVE APPARATUS OF RUMINANTS. 



261 



according as it has been submitted to the second mastication, or not. 

 The oesophagus (Fig. 77, a) does not terminate at its opening into the 

 first stomach or paunch (5), but it is continued onwards as a deep 

 groove with two lips (Fig. 78): by the closure of these lips it is made 

 to form a tube, which serves to convey the food onwards into the 

 third stomach ; but when they separate, the food is allowed to pass 

 either into the first or the second stomach. When the food is first 

 swallowed, it undergoes but very little mastication ; it is consequently 

 firm in its consistence, and is brought down to the termination of the 

 oesophagus in dry bulky masses. These separate the lips of the groove 

 or demi-canal (Fig. 78, e, e\ and pass into the first and second stomachs. 

 After they have been macerated in the fluids of these cavities, they are 

 returned to the mouth by a reverse peristaltic action of the oesophagus ; 

 this return, takes place in a very regular manner, the food being shaped 

 into globular pellets by compression within a sort of mould formed by 



Fig. 78. 





Section of part of the Stomach of the Sheep, to show the demi-canal of the oesophagus; the mucous mem- 

 brane is for the most part removed, to show the arrangement of the muscular fibres. At a is seen the 

 termination of the oesophageal tube, the cut edge of whose mucous membrane is shown at b. The lining ot 

 the first stomach is shown at c, c ; and the mucous membrane of the second stomach is seen to be raisec 

 from the subjacent fibres at d. At e, e, the lips of the demi-canal are seen bounding the groove, at B 

 lower end of which is the entrance to the third stomach or many-plies. 



the demi-canal, and these pellets being conveyed to the mouth at regular 

 intervals, apparently by a rhythmical movement of the oesophagus. It 

 is then subjected to a prolonged mastication within the mouth (the 

 "chewing of the cud"), by which it is thoroughly triturated and im- 

 pregnated with saliva ; after which it is again swallowed in a pulpy 

 semi-fluid state. It now passes along the groove which forms the con- 

 tinuation of the oesophagus, without opening its lips ; and is thus con- 

 veyed into the third stomach (Fig. 77, d\ whence it passes to the fourth 



