THE DIGESTIVE APPARATUS IN BIRDS. 435 



the spleen and left kidney. Its texture is consistent, and of a greyish-white colour. The 

 duct of Wirsung terminates along with the ductus choledochus in the ampulla of Vuter. 



3. Spleen. This is not falciform, but quadrangular ; its inferior extremity is larger 

 than the superior. It is attached to the stomach by the great omentum, and its inner 

 face is divided iuto two portions by a salient ridge ; a little in front of this is a fissure, 

 the hilum lienis, by which vessels enter it. 



CHAPTER III. 



THE DIGESTIVE APPARATUS OF BIRDS. 



CONSTRUCTED on the same plan as that of Mammals, the digestive apparatus of Birds 

 nevertheless offers in its arrangement several important peculiarities, which will be 

 hurriedly noticed in reviewing, from the mouth to the anus, its different sections. 



Mouth. The essentially distinctive character of the mouth of birds consists in the 

 absence of lips and teeth, these organs being replaced by a horny production fixed 

 to each jaw, and forming the salient part termed the beak. In the Gallinacse, the beak 

 is short, pointed, thick, and strong, the upper mandible being curved over the lower. In 

 Palmipeds, it is longer, weaker, flattened above and below, widened at its free extremity, 

 and furnished within the mouth, on the borders of each mandible, with a series of thin 

 and sharp transverse laminae to cut the herbage.^ 



The muscular appendage, or tongue, lodged in the buccal cavity, is suspended to a 

 remarkably mobile hyoidean apparatus. Covered by a horny epithelium, and provided at 

 its base with several papillae directed backwards, this organ always affects the form of 

 the lower jaw : in Poultry it is like the barbed head of an arrow, the point being directed 

 forwards ; in Pigeons this saggital form is still more marked ; in Geese and Ducks, on 

 the contrary, and in consequence of the wide shape of the beak, it has not this disposition, 

 and is softer and more flexible than in the Gallinaoge. 



"With regard to the salivary glands annexed to the mouth, they are imperfectly 

 developed, the presence of the fluids they secrete being less necessary in birds than in 

 Mammals, as the food is nearly always swallowed without undergoing mastication; 

 consequently insalivation is all but useless. 



Gurlt 1 speaks of a parotid gland situated beneath the zygomatic arch, whose duct 

 opens into the mouth behind the commissure of the jaws. Meckel names this organ the 

 angular gland of the mouth, and says that it is difficult to regard it as representing the 

 parotids, any morethan the glands of the cheeks and lips. Duvernoy 2 categorically 

 assimilates it to the latter. 



The sublingual glands lie in the median line throughout nearly their whole extent, 

 and form an apparently single and conical mass, whose apex occupies the re-entering 

 angle formed by the union of the two branches of the lower maxilla. 



According to Duvernoy, the submaxillary glands are represented by two very small 

 organs situated behind the preceding. Their existence, however, is far from being 

 general ; for among common poultry, the Turkey was- the only bird in which Duvernoy 

 observed these submaxillary glands. 



PHARYNX (Fig. 221, 2). This cavity is not distinct from the mouth, the soft palate 

 being entirely absent in birds. On its superior wall mav be remarked the guttural orifice 

 of the nasal cavities : a longitudinal slit divided into two by the inferior border of the 

 vomer. Below is another less extensive slit, the entrance to the larynx, and which is 

 remarkable for the complete absence of the epiglottidean operculum. 



(ESOPHAGUS. This canal is distinguished by its enormous calibre and great expansi- 

 bility. Its walls are very thin, and contain in their substance lenticular glands, easily seen 

 in an inflated oesophagus, in consequence of the tenuity and transparency of its textures. 



At its origin, the cesophageal canal is not separated from the pharynx by any 

 constriction ; in its course it lies alongside the long muscle of the neck, and the trachea ; 

 its terminal extremity is inserted into the first compartment of the stomach, or succentric 

 ventricle, alter entering the thorax and passing above the origin of the bronchi, 

 between their two branches. 



In Palmipeds, the oesophagus is dilated in its cervical portion in such a manner as 

 to form, when its walls are distended, a long fusiform cavity. 



1 * Acatomie der Hausvogel.' Berlin, 1849. 



2 Cuvier. * Anatomie Comparee.' 2nd Edition. Pari?, 1836. 



