INTESTINES OF BIRDS. 167 



precla viventibus, si aurem prope admoveris clum ventriculus je- 

 juniis est, manifestos intus strepitus lapillorum illuc ingestorum, 

 invicemque collisorum, percipias.' And Hunter observes {Animal 

 (Economy, 4to, p. 198), ' The extent of motion in grindstones need 

 not be the tenth of an inch, if their motion is alternate and in 

 contrary directions. But although the motion of the gizzard is 

 hardly visible, yet we may be made very sensible of its action by 

 putting the ear to the sides of a fowl while it is grinding its food, 

 when the stones can be heard moving upon one another.' Tiede- 

 mann believed that the muscles of the gizzard were in some degree 

 voluntary, having observed that when he placed his hand opposite 

 the gizzard, its motions suddenly stopped. 



The pyloric orifice of the gizzard is guarded by a valve in many 

 Birds, especially in those w^hich swallow the largest stones. This 

 valve in the Ostrich is formed by a rising of the cuticle divided 

 into six or seven ridges, which close the pylorus like a grating, 

 and allow only stones of small size to pass through. In the 

 Touraco the pylorus projects into the duodenum in a tubular form. 

 There is a double valve at the pyloric orifice in the Gannet, and 

 a single large valvular ridge at the same part in the Gigantic 

 Crane. In this species and some other Waders, as the Heron 

 and Bittern ; also in the Pelican, and, according to Cuvier, in 

 the Penguin and Grebe, there is a small but distinct cavity inter- 

 posed between the gizzard and intestine. The analogous struc- 

 ture has been described in the Crocodile (vol. i. p. 442, fig. 

 298, g). 



The intestines reach from the stomach to the cloaca ; in relative 

 length they are much shorter than in the Mammalia. In the 

 Toucan, for example, the whole intestinal canal scarcely equals 

 twice the length of the body, including the bill. The canal is 

 divided into small and large intestines, sometimes by an internal 

 valve, sometimes by the insertion of a single coecum, but most 

 generally by those of two cocca, which are always opposite to one 

 another. In a few instances there is no such distinction. The 

 small intestines and coeca are longest in the vegetable feeders. 

 The large intestine is, with one or two exceptions, very short and 

 straio^ht in all Birds. 



The course of the small intestine varies somewhat in the dif- 

 ferent orders of Birds ; it is always characterised by the elongated 

 fold or loop made by the duodenum, fig. 85, /, /, which fold re- 

 ceives the pancreas, ib. q, q, in its concavity. 



In the Raptores the intestines are generally disposed as fol- 

 lows : — 



