AVES. 



323 



is only twice the length of the body, except in 

 the fish-eating Osprey, in which the intestines 

 are very narrow, and are to the length of the 

 bird itself as eight to one. 



In the Insessores the scolloped folds of the 

 small intestine are narrower and longer than in 

 the Raptores, and the ileum generally adheres 

 to the duodenal mesentery and pancreas in- 

 stead of to the stomach, prior to passing down 

 to form its last fold and to terminate in the 

 rectum. In the Raven the small intestines are 

 disposed at their commencement in concentric 

 folds. 



Among the Scansores the Cuckoo presents 

 the following disposition of the intestinal 

 canal : after the usual long and narrow duo- 

 denal fold, the ileum* makes a fold which is 

 widened at the end, it then forms a close fold 

 upon itself, at the termination of which the 

 rectum commences. In the Maccaw the 

 course of the small intestine is somewhat 

 peculiar: after forming the duodenal fold, 

 it is disposed in three distinct packets of 

 folds : the intestine, after forming the first two, 

 passes alternately from one to the other, de- 

 scribing shorter folds upon each ; it then forms 

 the third distinct fold, which is a long one, 

 at the termination of which the ileum adheres 

 closely to the right side of the gizzard, and then 

 passes backwards and dilates into the rectum. 



In the Rasores the Dove-tribe have the 

 small intestines disposed in three principal 

 folds ; the first is the duodenal fold (ff, fg. 

 163); the second is along and narrow fold, 

 coiled and doubled upon itself, with the turns 

 closely connected together, ( k, fig. 163) ; the 

 third is also a long fold, which is bent or 

 twisted, (k', fg. 163.) In the common Fowl 

 the duodenum is disposed in a long simple 

 loop; the ileum passes towards the left, and is 

 disposed in loose folds on the right and lower 

 edge of the mesentery ; the ileum before its 

 termination passes up behind the preceding 

 folds, and is accompanied as far as the root 

 of the mesentery by the two cceca, which 

 there open into the commencement of the large 

 intestine. 



The Ostrich presents the most complicated 

 course of the intestinal canal in the whole 

 class of birds. The duodenal fold is about 

 a foot in length, and the returning part makes 

 a bend upon itself before it reaches the py- 

 lorus ; the intestine then turns down again 

 behind the duodenal folds and gradually ac- 

 quires a wider mesentery. The ileum after a 

 2w folds ascends towards the left side, accom- 

 panied by the two long cceca, and becomes 

 again connected with the posterior part of the 

 duodenal mesentery ; beyond which the coeca 

 enter the intestine behind the root of the me- 

 sentery, and the large intestine commences, 

 part differs from the rectum in other 

 an ds in its great extent, being nearly double 

 the length of the small intestines, and being 



isposed in folds upon a wide mesentery. It 

 terminates by an oblique valvular aperture in 

 a large urinary receptacle. In the Bustard the 



There is seldom any part of the small intestine 

 mpty so as to merit the n?une of jejunum. 



rectum is a foot in length, which is the nearest 

 approach to the Ostrich which the rest of the 

 class make in this respect. 



The small intestines in the Grallatores are 

 characterized by their small diameter and long 

 and narrow folds ; these are sometimes ex- 

 tended parallel to one another, as in the Crane 

 and Coot; or folded concentrically in a mass, 

 as in the Curlew and Flamingo. In the latter 

 species the duodenal fold is four inches in 

 length ; then the small intestines are disposed 

 in twenty-one elliptical spiral convolutions, 

 eleven descending towards the rectum and ten 

 returning towards the gizzard in the interspaces 

 of the former. 



Many of the Nutatores present a concentric 

 disposition of the folds of the small intestines 

 similar to the Flamingo. Home* has given 

 figures of this structure in the intestines of the 

 Sea-mew (pi. cviii.) ; the Gannet or Solan 

 Goose (pi. cvi.); and the Goose (pi. cxi.). 

 It likewise obtains in the Pelecan and Cor- 

 morant. 



The arrangement of the muscular fibres of 

 the intestine is the same as in the oesophagus, 

 the external layer being transverse, the internal 

 longitudinal. 



The villi of the lining membrane manifest an 

 analogy with the covering of the outer skin, 

 being generally much elongated, so as to pre- 

 sent a downy appearance when viewed under 

 water. There are, however, great varieties in the 

 shape and length of the villi. In the Emeu 

 they consist of small lamellae of the lining 

 membrane folded like the frill of a shirt. In 

 the Ostrich the lamellae are thin, long, and nu- 

 merous. In the Flamingo they are short and 

 arranged in parallel longitudinal zig-zag lines. 



In many birds a small diverticulum is ob- 

 served in the small intestine, which indicates 

 the place of attachment of the pedicle of the 

 yolk-bag in the embryo (m, jig. 157). We 

 have found this process half an inch in length 

 in the Gallinule, and situated seventeen inches 

 from the pylorus. In the Bay Ibis ( Ibis falci- 

 nellaj the vitelline ccecum is an inch in length. 



The birds in which the cceca coll have been 

 found wanting are comparatively few, though 

 such examples occur in all the orders. These 

 exceptions are most frequent among the Scan- 

 sores, in which the coeca are absent in the Wry- 

 necks, the Toucan s, theTouracos, the Parrot tribe, 

 and according to Cuvier in the Woodpeckers.f 

 In the Insessores the cceca are deficient in the 

 Hornbill and the Lark. Among the Gral- 

 latores, we have found them wanting in a Spoon- 

 bill. In the Natatores they are absent in the 

 Cormorant. The Herons, Bitterns, and, occa- 

 sionally, the Grebes afford the rare examples of 

 a single ccecum, which is also remarkably short. 



In the Raptores the diurnal and nocturnal 

 tribes differ remarkably in the length of the 

 cceca. They are each less than half an inch in 

 length in the Eagles and Vultures, but are occa- 

 sionally wanting in the latter. Cuvier states 



* Comparative Anatomy, vol. ii. 



t In the Poppinjay ( Picusviridis, Linn.^) we have 

 found two small cceca, so closely adhering to the 

 intestine as easily to be overlooked. 



Y 2 



