OCR Text |
Show 1896.] INTESTINAL TRACT OF BIRDS. 149 supplied by the posterior mesenteric vein. This structure is present in all the Accipitres I have examined, and Dr. Gadow states that all the Accipitres and Catharta? have irregular kinks above the rectum. A similar deviation occurs in the Petrels (fig. 7, p. 143). GALLIFORMES. I have not had the opportunity of dissecting any Galliformes except Galli. The figure of the young Argus Pheasant (fig. 2) may serve as a type for the adult intestine of the Peacocks, Fowls, Quails, Tragopans, and so forth. The three great portions of the intestine and the three great mesenteric veins are always present in the typical form. The adult shows the vestige of the yolk-duct at the end of the middle mesenteric vein. Branches radiate off from the middle vein to the irregular loops of the circular fold, and the last part of the circular fold, along which the enormous caeca lie, is drained partly by a recurrent branch of the middle mesenteric vein and partly by short-circuiting branches from the vein of the duodenum. The rectum is always straight. GRUTFORMES. Like the Galliformes, the Gruiformes closely conform to the primitive type. The gut is short, and instead of being thrown into a number of irregular minor loops the subsidiary loops are Fig. 13. Crex pratensis ; intestinal tract, x, short-circuiting vessel divided. few in number and definitely placed. The Common Land-Rail (fig. 13) may be taken as typical of the Eallidae. Porphryio and Aramides are practically identical with it, and the Cranes and Psophia differ only in minor particulars. The duodenum is a narrow regular loop : the circular loop is pulled out into four narrow subsidiary loops ; upon the distal limb of the second subsidiary loop the vestige of the yolk-duct is found. This is very large and is bound |