THE FROG ; VISCERA AND VASCULAR SYSTEM 47 



so that the prey adhere to it. Behind the angle of the jaw 

 is a region known as the pharynx^ into which open, at the 

 sides of its roof, the pair of Eustachian tubes which lead to 

 the drums of the ears, and below, in the male, a pair of vocal 

 sacs which are inflated and act as resonators during croak- 

 ing. In the middle of the 

 floor of the pharynx is a - e - 



slit-like opening, the glottis, 

 which leads into the wind- 

 pipe. 



From the pharynx a tube 

 known as the gullet or 

 oesophagus leads backwards 

 in the body cavity to the 

 maw or stomach, which is 

 spindle-shaped and separ- 

 ated by a slight constric- 

 tion, the pylorus, from the 

 bowel or intestine. The first 

 part of the intestine, known 

 as the duodenum, is narrow 

 and turns forward so as to 

 lie parallel with the stom- 

 ach. It is succeeded by 

 another narrow tube, the °'^' 

 ileum, which runs back- 

 wards in several coils. 

 Duodenum and ileum are 

 together known as the small 

 intestine-, at its hinder end FlG 23 _ A vertkal section through 



this region opens suddenly a tooth and part of the maxilla of 



into a much wider tube, the a frog. 



rectum. The length of the K Base of the t00thj composed of hone 



Small intestine is from 4 (cement); d., dentine; ;«., enamel; m, 



to 5 inches; that of the 



rectum is about an inch 



and a quarter. The internal surface of the intestine is 



increased by folds of its lining. These are transverse 



in the duodenum and longitudinal in the ileum. The 



rectum passes into a region known as the cloaca, which 



receives ventrally a thin-walled, bilobed sac, the urinary 



maxilla ; o.p.c, opening of the pulp 

 cavity. 



