24 IIIE rJi-VTlLERED TIUISES. 



occupies its usual situiitiou at the upper end of the windpipe, \\ hieh, however, is destitute 

 of the valve or lid, which is found in man. 



With such a view of the vocal organs in birds, we may consider their lungs and wind- 

 pipe as forming a natvu-al bagpipe, in which the lungs constitute the pouch, and supplj- 

 the wind ; the windpipe itself forming the chanter or pipe ; the lower or more compli- 

 cated part being the reed or moutli-pieee which produces" the simple sound ; and the 

 upper part the finger-holes, which modify the simple soimd into an infinite variety of 

 distinct notes. 



It has been remarked by Dr. ^Macartnej', that "a very little comparison of the 

 mechanism of -wind musical instrimients with the organs of the voice in birds, wiU show 

 how nearly they are allied to each other ; and it maj' be observed, that the sound 

 produced by some of the larger birds is exactly similar to the notes that proceed from a 

 clarionet or hautboy, in the hands of an untutored musician. The inferior glottis exactly 

 corresponds to the reed, and produces the tone or simjale soimd. The superior larynx 

 gives it utterance, as the holes of the instrument ; but the strength and body of the note 

 depend upon the extent and capacity of the trachea, and the hardness and elasticity of its 

 parts. The convolution and bony cells of the windpipe, therefore, may be compared with 

 the times of a French horn, and the divisions of a bassoon ; and they produce the proper 

 effects of these parts in the voices of 'those birds in which the}" are found. 



"When the food of birds requires insaliA'ation, it is performed in the crop (fig. 19, c), a 

 dilatation of the oesophagus copiously furnished with secreting follicles. In the rapacious 

 birds this is absent, or very slightly developed. The second stomach is the one in wliich 

 the o-astric juice appears to be formed. This is thoroughly incorporated with the 

 gizzard, ci, which is a hollow muscle, furnished with a hard tendonous lining, where by 

 the aid of little stones, gravel, and other hard substances, collected by the bird, the food 

 is efiectually groimd down. In this process it is aided by the gastric juice, which is said 

 to issue from another source, in the shape of an enlargement, not far distant from the 

 gizzard. If we go to the roosting-places of birds, while they are asleep, and place 

 the ear to their bodies, the grinding of the mill-like gizzard will be heard with the 

 utmost distinctness, and it will be found doing its work with surprising energy. Other 

 requisites are provided for perfect digestion, in its subsequent stages, as a liver, a gall- 

 bladder and a series of intestines. In carnivorous birds aU the receptacles are nearly 

 united in one ; a small thin muscle supplies the place of the gizzard, which is not required, 

 as the food is easily digested. The rcnuiinder of the intestine exliibits little dift'erence 

 until it approaches its outlet ; but in many of the graminivorous species there arc two 

 curious ai)i)endagcs, opening into the tube, the use of which is at present xniknown. 



The brain of birds (fig. 2U) is much larger than that of creatures inferior in the scale of 

 animal existence, filling up the whole of the cavity in which it is contained. The prinrijial 

 increase is manifested in the cerebral hemispheres, and these extend, not only laterally, 

 but so far backwards as nearly to cover the optic lobes, which, as well as the olfactory 

 ganglia, arc proportionately reduced in size. The ccrebelluin now exhibits a greatly 

 increased development, especially in birds of powerful fiiglit, aiul those wliicli remain 

 lono" on the wing. iStill the surface of the brain is not marked by convolutions ; and the 

 distribution of its fibres is very simple. The organ of vision is ])recisely adapted to the 

 circimistances and necessities of birds. Tlie substance of the ej'e is more hard and liornj- 

 than it is in other instances, which compensates for the danger to which it is exposed by 

 its unusual prominence. Tlius eiulowed, as Audubon states, the pigeon is enabled, as it 

 travels with great speed, so inspect the countiy below, and discover its food with facility. 

 He observed, that when theso birds traverse barren rocks, they keep high in the air, to 

 de.scry distant lands ; whereas, when tlie enundy is fertik', tliey ily lower, to fix on the 

 part iu<j8t plentifully supplied with food. 



