320 



AVES. 



in a zonular form : they are chiefly remarkable 

 for their large cavity and wide orifice. In the 

 Common Fowl and Turkey the glands are more 

 complex, and form a complete circle. 



In the Cursors* the arrangement of the glands 

 is different in almost every genus. 



In the Ostrich they are of an extremely 

 complicated structure, and are extended in 

 unusual numbers over an oval space on the 

 left side of the proventriculus, which reaches 

 from the top to the bottom of the cavity, and 

 is about four inches broad. 



The llhea differs from the other Struthious 

 birds in having the solvent glands aggregated 

 into a single circular patch, which occupies 

 the posterior side of the proventricular cavity. 



In the Emeu the gastric glands are scattered 

 over the whole inner surface of the proven- 

 triculus, and are of large size ; they terminate 

 towards the gizzard in two oblique lines. 



In the Cassowary the glands are dispersed 

 over the proventriculus with a similar degree 

 of uniformity ; but they are smaller, and their 

 lower boundary is transverse. 



Among the Grallatores, the Marabou, or 

 Gigantic Crane, (Ciconia Argala and Ma- 

 rabou,) has the nearest affinity to the Rhea 

 in the structure and disposition of the gastric 

 glands ; they are each composed of an aggre- 

 gate of five or six follicles, terminating in the 

 proventriculus by a common aperture; and 

 they are disposed in two compact oval masses, 

 one on the anterior, the other on the posterior 

 surface of the cavity. In the Heron (Ardea 

 cineria) the solvent glands are of more sim- 

 ple structure, and are more dispersed over the 

 proventriculus; but still they are most nume- 

 rous on the anterior and posterior surfaces. 

 In the Flamingo the gastric glands are short 

 and simple follicles, arranged in two large oval 

 groups, which blend together at their edges. 



The Natatores present considerable differ- 

 ences among themselves in the disposition of 

 the solvent glands. In the Cormorant (Pha~ 

 lacrocorax carbo) they are arranged in two 

 circular spots, the one anterior and the other 

 posterior; while in the closely allied genus 

 the Sula, or Gannet, they form a complete belt 

 of great width, and consequently are extremely 

 numerous. In this respect the Gannet, or 

 Solan Goose, has a nearer affinity to the 

 Pelecan, with which both birds were generically 

 associated by Linnaeus. 



In the Sea-Gulls the gastric glands form a 

 continuous zone ; and in the Little Auk ( Alca 

 Alle) they are spread, according to Sir Everard 

 Home, over a greater proportional extent of 

 surface than in any other bird that lives on 

 animal food, and the form of the digestive 

 organs is peculiar to itself. The cardiac cavity 

 or proventriculus appears to be a direct con- 

 tinuation of the oesophagus, distinguished from 

 it by the termination of the cuticular lining and 

 the appearance of the solvent glands. The cavity 

 is continued down with very gradual enlar^e- 

 ment below the liver, and is then bent up to 

 the right side, and terminates in the gizzard. 

 The solvent glands are situated at the an- 

 terior or upper part of the cavity every where 



surrounding it, but lower down they lie prin- 

 cipally upon the posterior surface, and where 

 it is bent upwards towards the right side they 

 are entirely wanting. In the graminivorous 

 lamellirostral Water-birds, as the Swan, Goose, 

 &c. the gastric glands have a simple elongated 

 exterior form, but have an irregular or cellular 

 internal surface : they are closely arranged so 

 as to form a complete zone. 



In general the muscular or pyloric division 

 of the stomach immediately succeeds the glan- 

 dular or cardiac division ; but in some Birds, 

 as the Auk and Parrots, there is an intervening 

 portion without glands. It is always widely dif- 

 ferent in structure, and hence has received a dis- 

 tinct name, the 'gizzard' (gigerium, ventriculus 

 bulbosus). 



The gizzard is situated below or sacrad of 

 the liver, on the left side and dorsal aspect of 

 the abdomen, generally resting on the mass 

 of intestines ; although, according to Blumen- 

 bach, the Nutcracker and Toucan, as well as 

 the Cuckoo, differ in having the gizzard situated 

 on the abdominal part of the cavity. Hence 

 this peculiarity not being restricted to the Cuc- 

 koo affords no explanation, as has been sup- 

 posed, why it should not incubate. In the Owl, 

 also, the gizzard adheres to the membrane cover- 

 ing the internal surface of the abdominal muscles. 



In all birds the gizzard forms a more or less 

 lengthened sac, having at its upper part two 

 apertures ; one of these is of large size, com- 

 municating with the proventriculus (a, fig. 161, 

 162), the second is in close proximity with, 

 and to the right side of the preceding, leading 

 to the duodenum (b, fig. 161); below these 

 apertures the cavity extends to form a cul-de- 

 sac (c, fig. 161, 162.) At the middle of the 

 anterior arid posterior parts of the cul-de-sac 

 there is a tendon (e, fig. 156, 157) from which 

 the muscular fibres radiate. 



Fig. 161 



Gizzard of a Swan. 



