DIGESTIVE SYSTEM OF BIRDS. 157 



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. 



The S^vift presents an analogous dilatation of the faucial mem- 

 brane 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 "sving. A similar structure obtains in the Rook, 

 and probably in other Insectivorous Birds. It is notable in the 

 JSTutcracker ( Caryocatactes) ; which, descending from its favourite 

 snowy altitudes, may be seen to return with a swelling like an 

 enormous goitre as big as the head, formed by the gular pouch, 

 crammed with nuts.' 



The oesophagus, H, fig. 94, «, fig. 78, like the neck, is usually 

 very long in Birds : as it passes do^vn, it generally inclines to- 

 ward the right side; it is partially covered by the trachea, G^ 

 fig. 94, and connected to the surrounding parts by a loose cellu- 

 lar tissue. It is wide and dilatable, corresponding to the imper- 

 fection of the oral instruments as comminutors 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 Swimmers as a temporary re- 

 pository of food. 



When the Cormorant has by accident SAvallowed 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 Gannet 

 the oesophagus is extremely 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 diameter of 

 the gullet does not exceed half an inch, being suited to the 



» When writing the article Aves for the ♦ Cyclopedia of Anatomv,' in 1835, I had 

 not dissected a male Bastard, and introduced the old figure from ' Edwards's Nat, Ilist. 

 vol. ii. tab. 73 (1747),' fig. 54, with the current story of the sub-gular water-pouch, 

 Avhich Edwards derived from the anatomist Douglas. In 1848 I had the desired 

 opportunity and made the preparation, No. 772, q, described in the ' Physiological 

 Catalogue of the Ilunterian Collection.' The supposed gular pouch is a large cervical 

 air-cell, fig. 54, a, capable of inflation and singularly swelling out the neck in the 

 amorous male Bustard. See xxxviii*. 



