SPLANCHNOLOGY 



The Digestive Apparatus. This apparatus, apparatus digestorius, 

 consists of the organs directly concerned in the reception of food, in 

 its passage through the body, and in the expulsion of the unabsorbed 

 portion. For convenience, these organs are grouped as follows: the 

 alimentary canal and the accessory organs. 



The alimentary canal is a tube which extends from the mouth to 

 the anus. It has a complete lining of mucous membrane, external 

 to which is an almost continuous muscular coat. The abdominal 

 portion of the tube is largely covered with a serous membrane, the 

 visceral peritoneum. The canal consists of the following consecutive 

 segments: mouth, pharynx, first portion of the esophagus, crop, 

 second portion of the esophagus, proventriculus, gizzard, small 

 intestine, large intestine, and cloaca. 



The accessory organs are beak, tongue, salivary glands, liver, and 

 pancreas. 



The Mouth (Fig. 27). The distinctive character of the mouth 

 of the fowl consists, in the absence of lips and teeth and instead of 

 jaw bones of other animals, of a beak. The edge of the beak is 

 covered by a horn-like gum. The shape of the beak differs in the 

 various classes of birds. In the chicken the beak is short, strong, 

 thick, and pointed; in palmipeds it is flattened. The upper mandi- 

 ble extends out over the lower mandible. The outer portion of the 

 upper and the lower beaks is covered by a horny sheath. There 

 is no velum, and the mouth cavity is extended rather continuously 

 into the pharynx (Fig. 27, No. 4). The posterior cross bar of the 

 hard palate (Fig. 27, No. 5), which possesses a row of filiform papillae 

 projecting backward, marks the upper boundary line of the mouth; 

 while the posterior end of the tongue (Fig. 27, No. 6), likewise with 

 a row of filiform papillae, marks its lower boundary line. 



Paris of the Mouth. The mouth of fowls is divided into an upper 

 and a lower half. The upper half is divided into an anterior and a 

 posterior part. 



The anterior part extends from the anterior tip of the beak to the 

 posterior nares. It is further divided into an outer hard part and 



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