INTRODUCTION. 
XXlll 
great and disproportionate size of the cortical, compared with the 
medullary substance; whereas in man the latter is found in a greater 
quantity than the former; yet, if the whole of the brain of many of 
the smaller species of birds, such as the Sparrow, Chaffinch, and Goldhnch, 
be placed in the scale against the brain of Man, it will far exceed his, in 
proportion to the size of their respective bodies. The skeletons of birds 
are principally distinguished from those of the Mammalia by a skull, over 
which, in adults, there do not appear any real sutures ; by a horny appendage 
to the mouth, called the bill, uniformly without teeth ; by a moveable 
upper jaw ; by a small bone nearly square, by which the lower jaw is 
articulated with the cranium ; by not having an os interm axillare ; which 
is also wanting in Man, and some of the Monkey tribes ; and by having 
only one occipital condyle ; by the dorsal vertebrae being immovable, and the 
cervical vertebrae exceeding seven, the common number in the Mammalia 
(with few exceptions) ; by the small number of their ribs; by a sternum 
prolonged below into a vertical process ; by a pelvis open in front ; and by 
clavicles. From their simple conformation, birds are subject but to few 
diseases, and yet are liable to an annual change of their plumage, which 
generally happens in the autumnal season, or, according to a common pro- 
verb, “ in blackberry time,” though the Cuckoo, and some few others, moult 
in the spring. In cold climates, birds are said to change their plumage twice 
in a year. From the continual attrition which their clothing undergoes, it 
must necessarily sustain considerable injury. Ta obviate this defect, and 
to make it adequate to the wants of the animal, especially to give it a 
Blumenbach on Comp. Anat. 
** While labouring under the severity of this disordered state, the Cock ceases to crow, its 
spirits flag, it is no longer seen strutting exultingly in measured pace among the hens ; it retires 
to some sheltered corner to conceal itself; its comb and v^attles lose their bright red, and assume 
a pale brown colour; its eyes are sunk and hollow; it moves heavily; indeed all its actions display 
the debility of its body, and the decrease of those active stimulants, that are at once the source of 
motion and life. 
