column. With this column the broad ribs unite in the back, while in front they are held together by the sternum; and to make this cradle of bones more compact and fit to resist the action of the wings, and to protect the interior organs, the ribs touch each other with what the anatomists call "uncinate processes." Whoever is called upon to carve at the table a chicken or a turkey will experience how solid and protective the construction of the skeleton of the body is.
If the main body is in this way compact and immovable, some other part must be so much the more flexible, and this is the neck. If we watch a swan oiling its feathers with its bill, see the cervical evolutions of a flamingo, or an owl sitting with its head reversed, we are apt to experience a painful sensation in our necks and may wonder whether the bird will assume its normal position without breaking something. But all these motions are executed with the most perfect ease and security, and the construction of the vertebræ, which enables the birds to perform them, is simple and effective. These vertebræ do not articulate with each other by plain faces as the vertebræ in our bodies, but the articulations are saddle-shaped, so that the prominence of one vertebra fits into the excavation of the next one, and vice versa. If we take two adjoining vertebræ of the neck of a bird and try their motion, we shall find that this articulation admits two ways of turning—from 
Fig. 1.—Vertebra of a Bird with Saddle-shaped Articular Face. one side to the other as well as up and down. This saddle shape of the articular face of the cervical vertebræ is found without exception in all existing birds and in no other animal.
There are other features which are met with in all birds and exclusively in them for instance, the plumage. The horny bill is without teeth. The vertebræ of the tail are grown together and form a plowshare-shaped bone. This bone supports the tail feathers, which can be opened and closed like a fan, and which serve as a rudder and a parachute. The bones of the anterior extremities are transformed in such a way that they form an excellent framework for the wings; but, although the anatomists
distinguish easily radius, ulna, digits, etc., one would hardly suspect that these wing bones are perfectly analogous to those in the fore-feet of quadrupeds, or in our arms and hands.
Now let us turn our attention to the reptiles which exist at the present time to the lizards, crocodiles, snakes, and turtles. These cold-blooded, scaly animals seem to have nothing at all in
