THE VERTEBRATE BODY 



333 



doses of poisons, if the liver did not have this property. Mercury, for 

 example, is stored in the liver and in the days when mercury compounds 

 were used extensively in medicine, the liver was often badly damaged 

 by the accumulation of excess mercury. After being filtered through 

 the liver, the food is carried to the heart and then, after a quick trip to 

 the lungs and back, it is carried by the arteries to all parts of the body. 

 The tips of the smallest arteries again enter a capillary network where 

 the food diffuses out through the capillary walls and into the body cells 

 through the cell membranes. 



Maxillary teeth 

 Sulcus marginals 

 Internal nares 

 Vomerine teeth 



Esophagus 

 Eustachian tube 



Glottis 



Tongue 



Fig. 23.3. The open mouth of the frog. 



Back in the ileum, the indigestible part of the food passes on into 

 the large intestine, which is greater in diameter than the small intestine. 

 This material is still liquid, but the large intestine continues to absorb 

 the water until the waste is in a semisolid condition. It is now referred 

 to as feces and is ready to be egested. In the frog the feces are dis- 

 charged through a cavity, the cloaca, to the outside. The cloaca also 

 receives and discharges the products of the excretory and reproductive 

 systems as well as the feces from the digestive system. 



When this system is compared with that found in man we find that, 

 although they are basically similar, there are some differences. Our 

 method of ingestion is quite different. A man's tongue is fastened at 

 the posterior end and has nothing to do with food getting. We have 

 four kinds of teeth which are used for biting and chewing food. This 



