ORDER ACCIPITRES. 103 



The action of the nictitating membrane is highly raechanica 

 and curious. Being partially pervious by light, it seems ne- 

 cessarily to be destitute of fleshy fibres, and could not, there- 

 fore, be attached in the ordinary way to a muscle. It is elastic, 

 and lies, when unexcited, drawn back in the angle of the eye, 

 but, when used, is put into action by two muscles attached to 

 the posterior part of the globe of the eye, one of which is com- 

 posed of fibres descending obliquely toward the optic nerve, 

 and terminating in a tendon of a peculiar character, having no 

 insertion or attachment, but forming a cylindrical canal, which 

 bends round the optic nerve. The other muscle is attached 

 above the eye, near the nose, and is composed of a little fibrous 

 cord, which passes under the eye, to the lower edge of the 

 nictitating membrane ; the action of these two muscles draws 

 the membrane across the eye. 



Of the construction of the ear, what has been said in the 

 text must suffice. The sense of hearing is very perfect in the 

 class ; smell, on the contrary, seems obtuse, except in the birds 

 of prey, particularly the vultures, Avhich seem led to their food 

 very much by this sense. The apertures of the nostrils vary 

 nevertheless in the different genera. 



From the make of the tongue, covered with corneous pa- 

 pillae, it does not seem probable that birds enjoy the sense of 

 taste in a very high degree ; and whether they are much 

 influenced in the choice of the food proper to each by this 

 sense, may be questioned. 



The insensibility of the feathers, and callous character of the 

 integuments in the parts without plumes, seem sufficiently to 

 evince that the sense of touch also in this class is very im- 

 perfect. 



A brief notice of the nature and construction of feathers, the 

 common integuments of this class, may not be without interest. 

 Surrounded as we are on all sides with works of wonder and 

 astonishment, some of such stupendous magnitude that the 

 mind cannot embrace them, and others so infinitely minute, 

 that it cannot seize them, it is perhaps but little surprising that 



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