Vm INTRODUOTION. 



Fissirostres, and in some Owls, the outer toe is directed 

 backwards ; in some it is disposed laterally, as in Muso- 

 phagidse and the I^uff-birds; whilst in one family only, 

 the Trogoris, the inner lateral toe is disposed backwards. 

 A membrane connects the base of the front toes in most 

 birds of prey, in some Gallinaceaj, and in many of the 

 Grallatores; and, in the Swimming-birds, is developed to 

 the end of tlie anterior toes in many, and in a few even 

 the hallux is united to the inner toe by a web. In 

 many, the outer toe is usually joined to the middle toe by 

 the whole of the first joint, and in some birds these digits 

 are joined for a great portion of their length, and which 

 are hence called syndactyle. 



After these remarks on the external anatomy of Birds, 

 a short account of their internal anatomy may be usefully 

 added. 



The cranium is enrly anchylosed, and is joined to the 

 first cervical vertebrae by an unpaired articular tubercle. 

 The greater part of the upper jaw is formed by the inter- 

 maxillary bones; it is slightly moveable, though not so 

 freely as tlie lower jaw. The connection between these 

 bones and the skull takes place through some elastic 

 laminae above, and internally by means of a moveable tym- 

 panic bone, the os quadratum, which represents the drum 

 of the ear. 



The cervical vertebrse vary greatly in their length as 

 well as in their number, which vary from nine to twenty- 

 three (in the Swans only), the usual number being from ten 

 to fifteen. The neck, when long, is peculiarly flexible, capa- 

 ble not oidy of being bent forwards to the ground, but of 

 being doubled backwards when at rest. The trunk, on the 

 contrar}', requiring great solidity to serve as a fulcrum 

 for the action of the wings, the dorsal vertebra are ira- 



