NECK OF BIEDS. 51 



The ears of birds, within the bones of the head, arc 

 well formed ; but, with the exception of nocturnal 

 feeders, which are, of course, much guided by the 

 ear, they have little or no external concha. The 

 nocturnal ones (the owls especially) have external 

 ears ; but the openings of the ears of all birds are 

 concealed by feathers, generally of a more downy 

 character than those on the neighbouring parts. 

 These protect the ear from the violent action of the 

 air when the bird is in rapid flight, and also preserve 

 a uniform temperature in that delicate organ. 



THE NECK. 



The neck of birds does not, like that of the mam- 

 malia, consist of the same number of vertebrse in all 

 the species, but varies much according to the habit of 

 the bird. In some it is very long, and in others 

 moderate, but in all it is susceptible of much motion, 

 and of motion in all directions ; so that, generally 

 speaking, the point of the bill commands the whole 

 space within reach of the extended neck, and also all 

 parts of the body of the bird. The vertebree are also 

 articulated in such a manner as that the greatest and 

 most rapid flexures of the neck do not in the least 

 disturb the spinal cord or the circulation in the blood- 

 vessels. Neither does it, generally speaking, inter- 

 rupt the breathing by the windpipe ; though, as will 

 be explained in another section of this article, the 

 breathing of birds is not wholly performed through 

 that organ. 



As the bill of very many birds has to perform the 

 functions both of a mouth and hand, it becomes neces- 

 sary that the neck should be, in some respects, an 

 arm ; and it is a very convenient and efficient one. 

 The extent to which it can bend, not only without 

 e2 



