HOW ANIMALS EAT. 



73 



process of deglutition is in this wise : the food, masticated 

 by the teeth and lubricated by the saliva, is forced by the 

 tongue and cheeks into the pharynx ; the soft palate keep- 

 ing it out of the nasal aperture, and the valve-like epiglot- 

 tis falling down to form a bridge over the opening to the 

 windpipe. The moment the pharynx receives the food, 

 it is firmly grasped, and, the muscular fibres contracting 

 above it and left lax below it, it is rapidly thrust into the 

 oesophagus. Here, a similar movement (the peristaltic) 

 strips the food into the stomach. 34 The rapidity of these 

 contractions transmitted along the oesophagus may be ob- 

 served in the neck of a Horse while drinking. 



Deglutition in the Serpents is painfully slow, and some- 

 what peculiar. For how is an animal, without limbs or 

 molars, to swallow its prey, which is often much larger 

 than its own body ? The Boa-constrictor, e. g., seizes the 



Fio. 37.— Skull of Boa-constrictor: 1, frontal; 2, prefrontal; 4, postfrontal ; 5, basi- 

 occipital ; 6, sphenoid ; 7, parietal ; 12, squamosal ; 13, prootic ; 17, premax- 

 illary; 18, maxillary; 20, nasal; 24, transverse; 25, internal pterygoid; 34, den- 

 tary, lower jaw ; 35, angular ; 36, articular; a, quadrate; s, prenasal ; v, petrosal. 



head of its victim with its sharp recurving teeth, and 

 crushes the body with its overlapping coils. Then, slow- 

 ly uncoiling, and covering the carcass with a slimy mu- 

 cus, it thrusts the head into its mouth by main force, the 

 mouth stretching marvellously, the skull being loosely put 



