CH. VIIl] FROGS, TOADS, AND NEWTS 253 



the prey and preventing it from slipping out of the mouth; 

 they cannot be said to bite, either in the sense of cutting 

 or of grinding. The eye-balls however are very important 

 organs in gripping the prey in the mouth. At each gulp 

 made as a worm is being swallowed both eyeballs are 

 forcibly depressed into the mouth cavity, thrusting the 

 worm against the floor of the mouth and downwards into 

 the pharynx. If the worm chances to be decidedly upon 

 one side of the mouth the eyeball of that side alone is 

 depressed, the other remaining prominent. The toads 

 make use of their eyeballs in the same manner. 



There is no sharp line of demarcation between the 

 mouth, pharynx, and oesophagus (gullet), but the com- 

 mencement of the stomach is indicated by a decided curve 

 of the alimentary canal away from the median line towards 

 the left side of the body. The epithelium lining the mouth, 

 oesophagus, and parts of the stomach is ciliated; that of 

 the rest of the stomach is highly glandular ; no less than 

 four different types of gland have been described by various 

 authorities. The stomach lies almost parallel with the 

 long axis of the body, but turns slightly towards the right. 

 At its extreme right-hand end the circular muscle coat of 

 its wall is thickened to form the pylorus a ring of muscle 

 which acts as a guard at the junction of the stomach with 

 the small intestine and permits the passage of food in a 

 fine state of division only. The gastric juice is decidedly 

 acid and effects the solution of the shells of snails as well 

 as the digestion of proteid food substances. It seems 

 probable that the chitinous exoskeleton of insects is to 

 a large extent dissolved ; it is undoubtedly broken up and 



