96 OUTLINES OF NATURAL HISTORY. 



turned forwards and one backwards. The toe which 

 is turned backwards is really the innermost toe of the 

 foot (in man the "great toe"), and it is not only much 

 smaller than the others, but is raised above the ground, 

 so as to be comparatively useless. The three toes which 

 are turned forwards are all united with one another by 

 skin or membrane, so that the foot becomes " webbed," 

 and thus strikes the water like a broad paddle. The 

 feet and lower portions of the legs are also unfeathered, 

 and are protected by horny plates. 



The head carries the eyes, the openings of the ears 

 (concealed beneath the feathers), and the bill. The eyes 

 are furnished with an upper and lower eyelid, and also 

 with a third eyelid, which can be drawn across the 

 eye from the inside, so as to protect the organ from an 

 excess of light. 



The bill is composed of the upper and lower jaws, 

 encased in horn, and quite destitute of teeth. The lower 

 jaw is united to the skull, much as we saw in the serpent, 

 by means of the peculiar bone, which is termed the 

 " quadrate bone." On the top of the upper half of the 

 bill, at about its middle, we see the openings of the 

 nostrils, in the form of two oval slits. The bill is broad 

 and soft, only horny towards its margins, which are fur- 

 nished with numerous parallel transverse plates. Within 

 the bill is a large tongue, much more fleshy than is 

 ordinarily the case amongst birds. 



As regards the digestive system, the most noticeable point 

 is that a portion of the stomach is converted into an ex- 

 tremely strong muscular organ, which is termed the 

 "gizzard," and in which the food is ground down and 

 rendered fit for absorption into the blood. As the bird, 

 therefore, does not possess teeth, it may really be said to 

 chew its food in the gizzard. 



The blood is hot, and the heart is a four-chambered 

 organ, the two sides of which do not communicate in any 

 way. There is, therefore, no such mixture of the pure 

 and impure blood as takes place in Reptiles. 



The Goose, though to a great extent organised for an 



