AVES. 



317 



dular follicles are found abundantly developed 

 on the tongues of the Chelonian and Saurian 

 reptiles. Similar elongated follicles are situated 

 along the margin of the lower jaw, resembling 

 in their parallel pectinated disposition the bran- 

 chiae of Fishes. In the Goose the corresponding 

 follicles are longer and wider, and are situated 

 near the sides of the tongue. In the Raven these 

 mucous follicles are narrower but longer. 



The food, after being embued with the secre- 

 tion of the preceding glands, is poised upon 

 the tongue and swallowed partly by means 

 of the pressure of the tongue against the palate, 

 partly by a sudden upward jerk of the head. 

 The posterior apertures of the nostrils being 

 generally in the form of narrow fissures are 

 undefended by a soft palate or uvula ; and the 

 laryngeal aperture, which is of a similar form, 

 is in like manner unprovided with an epi- 

 glottis, but is defended by the retroverted 

 papillae at the base of the tongue. In many 

 birds, indeed, as the Albatross and Coot, there 

 is a small cartilage in the usual place of an 

 epiglottis, but insufficient to cover more than 

 a very small part of the laryngeal aperture. 

 Nitzsch has devoted a treatise to these rudimen- 

 tary epiglottides in Birds.* 



With respect to the fauces the remarkable 

 instance of a dilatation of these parts in the 

 Pelecan must not be forgotten. The exten- 

 sibility of the membrane between the rami of 

 the lower jaw admits of its formation into a 

 bag (, fig. 146), which is calculated to contain 

 ten quarts of water, and serves as a receptacle for 

 fishes, making in that state a conspicuous appen- 

 dage to the huge bill ; when empty it can be 

 contracted so as to be hardly visible. By means 

 of this mechanism a quantity of food can be 

 transported to the young ; and, as in disgorging 

 the bleeding fishes the parent presses the 

 bottom of the sac against her breast, this 

 action has probably given rise to the fable 

 of her wounding herself to nourish the young 

 with her own blood. 



A remarkable provision of an analogous na- 

 ture is met with in the Bustard as a sexual pecu- 



Iiarity(7/g.l55). In 

 the male there is a 

 membranous sac 

 extendingforsome 

 way down the an- 

 terior part of the 

 neck capable of 

 holding several 

 quarts of water ; 

 it communicates 

 with the mouth by 

 an aperture be- 

 neath the tongue. 

 It is not found ex- 

 cept in the mature 

 bird. It is sup- 

 posed to serve the 

 purpose of provid- 

 ing the female and 

 young during the 

 breeding season 



Fig. 155. 



Faucial bag of flu-. Bustard. 



Sec Meckel's Archiven, 1826, p. 613. 



with water, and hence may not be developed to 

 its full extent except at that period. 



The Swift presents an analogous dilatation of 

 the membrane of the fauces at the base of the 

 lower jaw and upper part of the throat: it is 

 most developed at the period of rearing the 

 young, when it is generally found distended 

 with insects in the old birds that are shot while 

 on the wing. This receptacle is of a rounded 

 form, and communicates with the fauces by 

 a wider opening than that of the Bustard ; it is 

 also proportionally of less extent. A similar 

 structure obtains in the Rook and probably in 

 other Insectivorous birds. 



The oesophagus (H, fg. 171 : a, fig. 156, 

 158), like the neck, is usually very long in birds : 

 as it passes down, it generally inclines towards 

 the right side ; it is partially covered by the tra- 

 chea (G,fig. 171), and connected to the sur- 

 rounding parts by a loose cellular tissue. It is 

 wide and dilatable, corresponding to the im- 

 perfection of the oral instruments as comminu- 

 tors of the food. In the rapacious and especially 

 in the piscivorous birds it is of great capacity, 

 enabling the latter to swallow the fishes entire, 

 and serving also in many Waders and Swim- 

 mers as a temporary repository of food. 



When the Cormorant has by accident swal- 

 lowed a large fish, which sticks in the gullet, 

 it has the power of inflating that part to its 

 utmost, and while in that state the head and 

 neck are shaken violently, in order to promote 

 its passage. In the Gaunet the oasophagus is ex- 

 tremely capacious, and, as the skin which covers 

 it is equally dilatable, five or six herrings may be 

 contained therein. In both these species it 

 forms one continued canal with the stomach. 



In the Flamingo, on the contrary, the dia- 

 meter of the gullet does not exceed half an inch, 

 being suited to the smallness of the objects 

 which constitute the food of this species. 



Besides deglutition the oesophagus is fre- 

 quently concerned in regurgitation ; and in 

 the Birds in which this phenomenon occurs, 

 the muscular coat of the gullet is well deve- 

 loped, as in the Ruminant Mammalia. The 

 Rdpiores, for example, habitually regurgi- 

 tate the bones, feathers, and other indiges- 

 tible parts of their prey, which, in the lan- 

 guage of the falconer, are called ' castings.' 

 A Toucan, which was preserved some years 

 alive in this country, was frequently observed 

 to regurgitate partially digested food, and after 

 submitting it to a rude kind of mastication by 

 its enormous beak, again to swallow it. 



The oesophagus possesses an external cel- 

 lular covering, a muscular coat, an internal 

 vascular tunic, and a cuticular lining. The 

 muscular coat consists of two layers of 

 fibres ; in the external stratum they are trans- 

 verse (, fig. 159), in the internal longitudinal 

 (b, Jig. 159); the reverse of the arrangement 

 observed in the human subject. 



Ingluvies. In those birds which are om- 

 nivorous, as the Toucans and Horn-bill?, in 

 the frugivorous and insectivorous birds, and in 

 most of the Grallatores, which find their food 

 in tolerable abundance, and take it in small 

 quantities without any considerable inter- 



