DIGESTIVE SYSTEM OP HYDROCORAX. 33 



short duct on the free surface of tlie membrane. The deeper cells of 

 the epithelium show round nuclei; these become flatter toward the free 

 inner surface, and at the surface they are almost as flat as those seen in 

 the skin. Apparently' only simple mucus for lubrication is secreted by 

 the lining of the cvsophagus. The photomicrograph shows the structures 

 quit« well. 



The proveutriculus is 30 millimeters in length and the wall is 8 

 millimeters thick in the thickest part, just above the sphincter muscle 

 which lies between it and the stomach. The inner surface is thickly set 

 with the mouths of glands and when examined in a recently collected 

 bird, is covered with a thick coat of sticky, nracoid material. On section, 

 an outer fibrous coat is seen; next a strong, circular, muscular layer; 

 then a longitudinal, muscular layer on which rests a layer of glands 

 beneath the mucosa. The glands of this layer are large, each is inclosed 

 in a connective tissue capsule and, somewhat like a salivary gland, 

 presents a radiating, tubular structui-e with a central space in which there 

 are verj' few cells and which is filled with mucoid material. Each gland 

 (or at least those of the inner layers), opens on the free surface of the 

 mucous membrane by a wide mouth, which passes through the mucosa 

 proper. They resemble "Brunner's" glands in that they lie below the 

 muscularis mucosas. Internal to this glandular layer is the mucosa 

 proper, of ordinary type, with villi projecting from the surface and with 

 a network of muscle fibers, forming a true, reticulate mmcularis mucosce. 



It is evident that the glandular layer of the proventrieulus is a highly 

 specialized structure, undoubtedly supplying the essential digestive fluid 

 for this part of the tract. This is the more certain when we remember 

 that the tough, deciduous membrane of the stomach, about to be described, 

 would effectively prevent any digestive fluid which might be secreted by 

 the glands of the' stomach from coming in contact with the food. 



The stomach of this large hornbill when empty, is oval with flattened 

 sides and varies in thiclmess from 2 millimeters on the membranous 

 sides, to 11 millimeters where the muscle is thickest. The muscle fibers 

 cross in a radiating manner from one tendinous disk to the similar disk 

 on the other side, and are reinforced by numerous other fibers arising 

 from the membranous, internal muscle-sheath. There is the usual 

 modification of fibers at the cardiac and pyloric openings and at the 

 cardiac opening a round, cord-like, circular muscle, 5 millimeters in 

 diameter, acts as a strong sphincter between the proventrieulus and 

 stomach. At the pyloric opening the sphincter is less well-marked. 



The entire lining of the stomach is corrugated and presents a brovniish, 

 irregular surface. On section this is seen to be due to the deciduails 

 membrane which, depending on its stage of development, is,' more or 

 less loosely attached to the stomach proper. The cardiac and pyloric 

 openings are but 15 millimeters apart. As the entire organ when empty 



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