A REPRESENTATIVE VERTEBRATE. FROG 



331 



racic and abdominal cavities. The thoracic 

 cavity contains the esophagus, trachea, 

 lungs, heart, and blood vessels. The abdom- 

 inal cavity contains the stomach, spleen, 

 pancreas, liver, gall bladder, kidneys, and 

 large and small intestines. The lower part 

 of the abdominal cavity is called the pelvic 

 cavity; this contains the bladder, rectum, 

 and some of the reproductive organs. 



Digestive system 



The principal functions of the digestive 

 system are to receive, digest, and absorb 

 food and eliminate some wastes. 



The food of the frog consists principally 

 of living worms and insects. These are usu- 

 ally captured by the extensile tongue, which 

 can be thrown forward as shown in the 



Subcutaneous lymph space 



Central cana 

 Muscle 

 Dorsal aorta 

 Posterior vena cava 



Mesentery 



Coelom 



Intestine 



Visceral peritoneum 



Skin 



Subcutaneous lymph space 



Spinal cord 



Vertebra 



Kidney 



Gonad 



Visceral peritoneum 



Lumen of Infestino 



Parietal peritoneum 



Abdominal vein 



Figure 213. Diagram of a cross section of the body of a frog through the kidneys and gonads 

 to show relation of the peritoneum (broken hues) to other organs. 



illustration at the head of this chapter 

 (headpiece). The object adheres to the 

 tongue, which is covered with a sticky secre- 

 tion, and is then drawn into the mouth. No 

 attention is paid to objects that are not mov- 

 ing. Large insects are pushed into the mouth 



with the forefeet. In case the object swal- 

 lowed proves undesirable, it can be ejected 

 through the mouth. 



The mouth cavity is large. The tongue 

 lies on the floor of the cavity with its an- 

 terior end attached to the jaw and its forked 



Hepatic 

 bile duct 

 Cystic duct 



Liver 



Hepatic 

 bile duct 



Ptincreas 



Pancreatic duct 



Stomach 

 Common bile duct 

 Duodenum 

 Ileum— 

 Pylorus 



Figure 214. Liver, gall bladder, pancreas, stomach, and part of the intestine of a frog. 



