COMPENSATION. 191 



state in -which they are cropped from the pasture or gathered 

 from the bundle. In the stomach they are softened by the 

 gastric juice, which in these animals is unusually copious. 

 Thus softened and rendered tender, they are returned a sec- 

 ond time to the action of the mouth, where the grinding teeth 

 complete at their leisure the trituration which is necessary, 

 but which was before left imperfect : I say the trituration 

 which is necessary, for it appears from experiments that the 

 gastric fluid of sheep, for example, has no effect in digesting 

 plants unless they have been previously masticated ; that it 

 only produces a slight maceration, nearly as common water 

 would do in a like degree of heat ; but that when once veg- 

 etables are reduced to pieces by mastication, the fluid then 

 exerts upon them its specific operation. Its first effect is 

 to soften them, and to destroy their natm-al consistency ; it 

 then goes on to dissolve them, not sparing even the toughest 

 parts, such as the nerves of the leaves. =* 



I think it very probable that the gratification also of the 

 animal is renewed and prolonged by this faculty. Sheep, 

 deer, and oxen appear to be in a state of enjoyment while 

 they are chewing the cud ; it is then, perhaps, that they 

 best relish their food. 



II. In birds, the comi^cnmtion is still more striking. 

 They have no teeth at all. What have they then to make 

 up for this severe want ? I speak of granivorous and herbiv- 

 orous birds, such as common fowls, turkeys, ducks, geese, 

 pigeons, etc. ; for it is concerning these alone that the ques- 

 tion need be asked. All these are furnished with a peculiar 

 and most powerful muscle, called the gizzard ; the inner 

 coat of which is fitted up with rough plaits, which, by a 

 strong friction against one another, break and grind the hard 

 aliment as effectually, and by the same mechanical action, 

 as a coffee-mill would do. It has been proved by the mf)s{ 

 correct experiments, that the gastric juice of these birds will 

 not operate u])on the entire grain ; not even when ?oftened 

 ■^ Spallanzar ?'. disc. 3, .sec. 140. 



