74 



VE ANATOMY. 



quarts of water; a similar provision is found in the swift, the rook, 

 the male bustard at maturity, and other insectivorous birds. The 

 alimentary canal is much longer and more capacious, and the glan- 

 dular apparatus better developed in the phytophagous birds than 

 in those which subsist more exclusively on animal food. The long, 

 wide, fleshy oesophagus, with a cuticular lining-, passes down 

 behind and to the right side of the trachea, behind the heart 

 and between the lungs. In rapacious birds it is capable of enor- 

 mous dilatation, but in the flamingo its diameter does not exceed 

 half an inch. In the frugivorous, insectivorous, and omnivorous 

 birds, the oesophagus presents nearly a uniform capacity all through, 

 but in the raptorial eagles and vultures, which gorge themselves at 

 uncertain periods, it forms a lateral dilatation at the lower part of 

 the neck termed the ingluvies or crop. And in those birds which 

 live exclusively on, and require to take a large quantity of vegetable 

 food, the crop is large, globular or oval, single in the common fowl, 

 and double in the pigeon ; it is altogether wanting in the swan and 

 goose. The oesophagus and crop are supplied with an abundant 

 mucous secretion, and are provided with an external circular and 

 an internal longitudinal set of muscular fibres, the reverse of the 

 disposition observed in the human subject. Mr. Hunter has re- 

 corded in his animal economy, some interesting observations on 

 the crop of the pigeon, from which it appears that this macerating 

 paunch takes on a secreting function during the breeding season, 

 and supplies the young pigeons with an abundance of milk, a diet 

 suitable to their tender a^e, and the analogy of the pigeon's milk to 

 that of the mammalia has not escaped popular notice. 



That part of the oesophagus which extends from the crop to the 

 gizzard, was called by Mr. Hunter the lower oesophagus ; at its in- 

 ferior part, just above the gizzard, it dilates into the glandular divi- 

 sion of the stomach, variously termed the jjroventriculus, ventri- 

 cular succenturiatus, bulbus glandulosus, echinus, infundibulum. 

 In the omnivorous and piscivorous tribes there is no perceptible 

 dilatation here, but in all it presents increased vascularity as it is 

 provided with a number of glands which secrete a fluid analogous 

 to the gastric juice. Beneath the infunbulum is the powerful 

 muscular gizzard directed transversely like the stomach of the 

 vertebrita, overlapped by the lobes of the liver, and lined internally 

 with a thick, dense epithelium. At the upper part of the gizzard 

 are two openings, one large, to the left side, and communicating 

 with the proventriculus, the other smaller, and a little to the right, 

 leads into the duodenum. In those birds which feed on grain and 

 other hard substances, the muscular fibres of the gizzard are dis- 

 tinguished by their density and red colour, they are arranged in 

 four masses, two lateral, called the digastric muscles, and connected 

 to anterior and posterior tendons, and two smaller ones between 

 these, at the end of the gizzard, termed musculi intermedii. In 

 rapacious and carnivorous birds the parietes of the gizzard are thin 

 and membranous, yet distinctly presenting the anterior and posterior 



