8 BIRDS. 



blood-vessels which supply the vascular nourish- 

 ing pulp of the barrel. When this pulp has 

 performed its office, and the stalk and other parts 

 of the feather are fully developed, it shrivels up 

 into the well-known substance, which every one 

 finds in a quill when he cuts it for the purpose of 

 making a pen."* 



As in the Mammalia, the classification of Birds 

 into Orders is founded upon the organs connected 

 with motion and food; that is to say, the charac- 

 ters are taken principally from the beak and feet. 

 The subordinate divisions depend chiefly upon 

 the form of the beak, and pass into each other by 

 almost imperceptible gradations, insomuch that 

 there is no other class of animals, in which the 

 genera and sub-genera are so little susceptible of 

 definite limitation. 



In the present work we shall adopt the Orders 



enumerated in the " List of the Genera of Birds" 



.of Mr. G. R. Gray, which are eight in number, 



viz., Accipitres, Passer es, Scansores, Columbce, 



Gallmce, Struthiones, Grallte, and Anseres. 



* Penny Cyclop. ; Art. BIRDS. 



