9b ANIMAL PHYSIOLOGY. 



into four compartments. When the ruminant is feeding, 

 the food passes into a large compartment, the paunch, 

 which is the cardiac extremity of the stomach, elongated and 

 folded on itself in foetal life, and subsequently much expanded. 

 When the animal lies down to ruminate, the contents of the 

 paunch are propelled in successive portions into a small com- 

 partment called the reticulum, from the honey-combed appear- 

 ance of its walls, and placed to the front below the oesophagus, 

 and by it are returned to the mouth in separate pellets. 

 After being a second time masticated, the food is again 

 swallowed, and being prevented by the closure of a ring of 



muscular fibres from re-entering 

 the first two compartments, it 

 falls into the third, the omasum, 

 which lies behind the second, 

 and is of similar size, but has 

 its mucous membrane thrown 

 into numerous broad folds 

 which separate up the bolus, 

 and allow it to pass in portions 

 Fig. 52. RUMINANT STOMACH, gradually into the fourth com- 

 cliagrammatic view. partment or abomasum, which 



is the pyloric end of the stomach, and the only part furnished 

 with a highly vascular and glandular mucous membrane. . 



The coecum may acquire a great development even in 

 animals in which the stomach is simple. This is the case 

 in the rabbit and in the horse, in both which it has great 

 width and length. Generally, the alimentary tube is much 

 more elongated and complex in vegetable-feeders than in 

 carnivora. 



65. Digestive Fluids. The first substance added to the 

 food is the saliva, which is furnished by three pairs of 

 compound sacculated or lobulated glands the p.arotid, the 

 submaxillary, and the sublingual. The parotid gland is 

 the largest, and is named from its nearness to the ear, lying 

 as it does in the hollow between the ear and the lower 

 jaw. It turns over the hinder border of the jaw; and 

 from this part of it issues a duct the duct of Stenson large 

 enough to admit a crow-quill, and opening into the mouth 

 through the cheek, opposite the second molar tooth of the 



