AND PHYSIOLOGY. 



191 



ever, three enlargements of the alimentary canal, all of which 

 prepare the food for assimilation. The first of these is the 

 u Xngluvies" or "Crop," where the food is softened by the 

 mucous secretion of the lining membrane. Then as it passes 

 along into the " Proventriculus,*' it receives the gastric juice 

 from the gastric glands which line it. The second stomach, 

 tho " Gizzard," i3 round and flat and made up of powerful 

 muscular fibres, except in birds of prey, where it is thinner 

 in texture. In gallinaceous birds its lining membrane is of 

 a horny consistency, which, with the powerful muscular fibres, 

 render it an organ of mastication to granivorous birds. Gravel 

 and angular stones are purposely swallowed by these birds 

 to aid in the digestive or grinding process. 



847. Teeth and Jaws of Reptiles.— Reptiles need teeth 

 only to seize and retain their prey, since whatever food is 

 taken by them, is swallowed without mastication, which is 

 one reason why the jaws and 

 throats of serpents are so 

 very capacious. A peculi- 

 arity in their bony construc- 

 tion renders this possible, 

 for the jaw is not made 

 up of one or at most two 

 pieces as in mammals, but of 

 several segments, which rea- 

 dily move one upon another, 

 as if with different articula- 

 tions. 



348. The Tongue —The Tongue is used as an instrument 

 for the capture of prey by many reptiles. Frogs and Sala- 

 manders are able to thrust it out with great rapidity and 



Give the names of each. Describe the Gizzard Why are gravel and stones swallowed 

 by granivorous birds? Which is the true stomach ? 347. What is the only use of teeth 

 in reptiles? State the reason why the jaws are so capacious. Of how many bones are 

 they frequently made up ? 318. Of what use is the tongue to some reptiles? 



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