NATURAL THEOLOGY. 303 



A gizzard is not found in birds of prey : their food 

 requires not to be ground down in a mill. The 

 compensatory contrivance goes no further than the 

 necessity. In both classes of birds, however, the 

 digestive organ within the body bears a strict and 

 mechanical relation to the external instruments for 

 procuring food. The soft membranous stomach 

 accompanies a hooked, notched beak ; short mus- 

 cular legs ; strong, sharp, crooked talons ; — the car- 

 tilaginous stomach attends that conformation of bill 

 and toes w hich restrains the bird to the picking of 

 seeds or the cropping of plants.oo 



^ We have said that it is the object to support animal hfe, and 

 to give the enjoyment of existence ; and that wherever the means 

 are afforded of converting a material under the processes of diges- 

 tion and assimilation, there animals will be found with an appa- 

 ratus of digestion adapted to the food. Nothing certainly can be 

 more curious than the vicarious action of the stomach and mouth. 

 We see, for example, that where the bill precludes mastication in 

 the mouth, it is performed in the stomach ; and then muscles are 

 found in the stomach as powerful as those of the jaws and teeth ; 

 and as to the teeth, or what is equivalent to them, Ave may say 

 that they are continually renewed. In fact, no mechanical struc- 

 ture of jaws and teeth could answer the purposes of nature here: 

 no union of bone and enamel in the tooth could have withstood 

 the attrition of the gizzard ; and one of the most beautiful and 

 interesting appliances of nature is the substitution, through the 

 instinct of the animal, of small stones of hard texture, generally 

 consisting of silex, introduced within the grasp and action of this 

 organ. It is a further proof that the mastication, if we may use 

 the term, is more perfect in the gizzard than where there is the 

 most complex structure of teeth, and therefore that is the means 

 of extracting the greater quantity of nutritious matter. Accord- 

 ingly, there are gizzards in most classes of animals. They are 

 not only found in birds, but in reptiles. The sea-turtle has what 



