344 TURKEY BUZZARD. 



The external nostrils, as already mentioned, occupy the whole 

 length of the nasal groove, being 6 twelfths of an inch long, of an 

 irregular oblong form, their greatest height 2^ twelfths, pervious or 

 communicating, the greatest breadth of the common space being 7 

 twelfths. Their posterior apertures. Fig. 5, are separated ^^S- *• 



by a strong dissepiment, and are of moderate size, but 

 without any appearance of the flap or operculum, which 

 many authors have mentioned as closing them. The 

 posterior or palatal aperture of the nares is also of moderate size, 

 linear-oblong, 6 twelfths in length, prolonged anteriorly into a slit 

 4i twelfths long, finely papillate on the edges. 



The nasal cavity. Fig. 4, cde, is large, of an irregular oblong compres- 

 sed form 10 twelfths in its greatest length, 7| in its greatest height. 

 There are two well-developed turbinated bones, de, of which the upper, 

 d, presenting the appearance of a hollow ovate body, forms two curves 

 upon itself, so that when the outer curve is cut open, it seems to contain 

 another oval body. The anterior or inferior spongy bone, e, is of an 

 elongated form, bent upwards, and forms a single curve on itself. Both 

 are only cartilaginous or membranous. The anterior extremity of the 

 hemisphere of the brain, b, is prolonged forwards between the orbits, 

 gradually tapering from a height of 3 twelfths to i twelfth, and ter- 

 minating in the olfactory nerve, which has ultimately a diameter of 

 a third of a twelfth, but is from the commencement divided into several 

 fibres, and is distributed upon the nasal cavity. A large branch of the 

 fifth pair,/, i twelfth in diameter, ascends across the orbit, enters the 

 nasal cavity, crosses the olfactory nerve, curves over the upper turbi- 

 nated bones, passes between the lower and the septum of the nasal 

 cavity, from which it emerges, enters the cavities of the supramaxil- 

 lary bone, and is distributed chiefly to the roof of the mouth, at g. The 

 anterior lobe-Uke process from the cerebral hemisphere, b, is in struc- 

 ture precisely similar to the part in its vicinity, and may be called the 

 olfactory lobe. It occupies the place which in most birds presents 

 merely a slender nerve, or filament inclosed in a bony tube traversing 

 the cellular osseous tissue, as is more especially seen in Owls and Goat- 

 suckers. 



The olfactory nerve has been ascertained in the mammalia to be the 

 instrument of smell ; but in the class of birds experiments and obser- 

 vations are wanting to determine its precise function, although analogy 



.:m 



