THE DIGESTIVE APPARATUS OF BIRDS. 515 



gizzard is only effected in Birds fed on hard coriaceous aliment, such as the 

 various kinds of grain. It would be useless in Birds of prey, in which the two 

 gizzard muscles are replaced by a thin fleshy membrane of uniform thickness — 

 showing that the presence of these muscles is subordinate to the kind of ahmentation. 



Intestine. — The length of the intestine varies, as in Mammals, according to 

 the nature of the food : very short in Birds of prey, it is notably elongated in 

 omnivorous and granivorous Birds. Its diameter is nearly uniform throughout 

 its whole extent, and it is difficult to establish in Birds the various distinctions 

 recognized in the intestine of Mammalia. It begins by a portion curved in a 

 loop, which represents the duodenum, the two branches of which, lying side by 

 side, are parallel to each other, like the cohc flexure of Solipeds. Fixed by a 

 short mesenteric frsenum to the colon, this part of the intestine includes the 

 pancreas between its two branches. Its curvature floats freely in the pelvic 

 portion of the abdominal cavity (Fig. 305, 8, 9, 10). 



To the duodenal loop succeed convolutions suspended to the sublumbar parietes 

 by a long mesentery, and which are rolled up into a single mass, elongated from 

 before to behind, occupying a middle position between the air-sacs of the 

 abdominal cavity. The analogy existing between this mass of convolutions, and 

 ths, floating portion of the small intestine of Mammals, does not require demonstration 

 (Fig. 305, 11, 12). 



The terminal part of this floating intestine lies beside the duodenal loop, and 

 is flanked by the two appendages disposed like cceca. These, scarcely marked in 

 the Pigeon by two small tubercles placed on the track of the intestinal tube, do 

 not measure less than from 6 to 10 inches in the other domesticated Birds ; 

 they are two narrow culs-de-sac, slightly club-shaped at their closed extremities, 

 which are free and directed towards the origin of the intestine, while the other 

 extremity opens into the intestinal canal near the anus. There are always 

 alimentary matters in these sacs, these becoming introduced, in following a 

 retrograde course, by the same almost unknown mechanism which presides over 

 the accumulation of spermatic fluid in the vesiculae seminales. According to the 

 majority of naturalists, these two appendages, although described as cceca, do not 

 represent the reservoir bearing that designation in Mammals. This reservoir is 

 nothing more than a small special appendix placed on the track of the intestine, 

 in front of the free extremity of the above-mentioned culs-de-sac, and is only to 

 be found in a small number of Birds, and among these sometimes, as Gurlt^ 

 affirms, is the Goose. According to this view, which appears to be a very 

 rational one, the portion of intestine comprised between the two blind tubes 

 annexed to the viscera (Fig. 305, 12') corresponds to the colon, and these tubes 

 themselves are only dependencies of this intestine. 



The rectum (Fig. 305, 15) terminates the digestive canal ; it is the short 

 portion of intestine that follows the opening of the caeca. Placed in the 

 sublumbar region, this viscus is terminated by a dilatation, the cloaca (Fig. 305, 

 16), a vestibule common to the digestive and genito-urinary passages, which 

 opens externally at the anus, lodges the penis when it exists, and serves as a 

 confluent for the ureters, oviduct, bursa of Fabricius, and the deferent canals. 



Abdominal Appendages of the Digestive Canal. — Lirer (Fig. 305, 19, 



20). — This is a voluminous gland, divided into two principal lobes — a right and 



left, the former always larger than the latter ; these incompletely include, on 



each side, the gizzard and succentric ventricle. In the Pigeon, this gland is 



» Gurit, Op. cit 



