THE WONDERS OF LIFE 



off of a pair of sacs (coelom-pouches) from the gut near 

 the mouth; the pouches touch, and then coalesce, as 

 their divipion - walls break down. If a part of the 

 dividing wall remains, it serves as mesentery to fasten 

 the gut to the body-wall. The action of the four 

 groups of alimentary organs remains very simple in the 

 lowest and oldest coelomaria, the worms (vermdlia); 

 but in the other higher animfils, which have been 

 evolved from these, they have very varied and often 

 complicated features. 



In the great majority of the coelomaria the gastric 

 system forms a highly differentiated apparatus, com- 

 posed, as in man, of a number of different organs. The 

 food is usually taken in by the mouth, ground up by the 

 jaws or th^ teeth, and softened with sajiva, which the 

 salivary glands pour into the cavity of the mouth. 

 From the mouth the pulpy food passes in swallowing 

 into the gullet, which often has glandular appgndages, 

 and from this through the narrow esophagus into the 

 stomach. This most important part of the alimentary 

 apparatus is often divided into several sections, one of 

 which (the masticating stomach) is armed with teeth 

 and prepared for a further triturition of solid pieces, 

 while the other (the glandular stomach) produces the 

 dissolving gastric juice. The liquefied food {chylus) 

 then passes into the small intestine (ileum) , which baa 

 to absorb it, and is as a rule the longest section of the 

 alimentary canal. A number of different digestive 

 glands open into this intestine, the most important of 

 them being the liver. The small intestine is often 

 sharply distinguished from the large intestine (colon), 

 the last large section of the alimentary canal; into this 

 also a number of glands and blind intestines open. The 

 last portion of it is called the rectum, and this removes 

 the indigestible remnants of the food (faeces) through 

 the anus. 



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