xm PHYLUM CHORDATA 385 



yellow or green colour : its cavity always contains small stones, 

 which are swallowed by the Bird to aid the gizzard in grinding 

 up the food. 



The duodenum (duo.} leaves the gizzard quite close to the 

 entrance of the proventriculus and forms a distinct loop enclosing 

 the pancreas. The rest of the small intestine is called the ileum 

 (Urn.) : it presents first a single loop ; then follows its greater part 

 coiled into a sort of spiral ; and lastly conies a single loop which 

 passes without change of diameter into the rectum (ret.), the 

 junction between the two being marked only by a pair of small 

 blind pouches or cceca (coe.). The cloaca is a large chamber divided 

 into three compartments, the coprodceum (cpdm.), which receives the 

 rectum, the urodceum (urdm.), into which the urinary and genital 

 ducts open, and the proctodceum (prdm.), which opens externally by 

 the anus. 



There are small buccal glands opening into the mouth, but none 

 that can be called salivary. The liver (Ir.) is large, and is divisible 

 into right and left lobes, each opening by its own duct (6. d. 1, 

 b. d. 2) into the duodenum : there is no gall-bladder. The pancreas 

 (pn.) is a compact reddish gland lying in the loop of the duodenum, 

 into which it discharges its secretion by three ducts (pn. d. 1-3). 

 A thick- walled glandular pouch, the bursa Fabricii (b. fabr.), lies 

 against the dorsal wall of the cloaca in young Birds and opens 

 into the proctodseum : it atrophies in the adult. 



Ductless Glands. The spleen (spl.) is an ovoid red body, of 

 unusually small proportional size, attached by peritoneum to the 

 right side of the proventriculus. There are paired thyroids at the 

 base of the neck ; and, in young Pigeons, there is an elongated 

 ihymus on each side of the neck. The adrenals (Fig. 1060, adr.) 

 are irregular yellow bodies placed at the anterior ends of the kidneys. 



Respiratory and Vocal Organs. The glottis (Fig. 1051, gl.) 

 is situated just behind the root of the tongue, and leads into the 

 larynx, which is supported by cartilages a cricoid divided into four 

 pieces, and paired arytenoids but does not, as in other Vertebrates, 

 function as the organ of voice. The anterior part of the trachea 

 (tr.) has the usual position, ventral to the gullet ; but further back 

 it is displaced to the left by the crop, becoming ventral once more 

 as it enters the body-cavity, where it divides into the right (r. br.) 

 and left bronchi. The rings supporting the trachea are not 

 cartilaginous but bony, as also is the first ring of each bronchus, 

 those of the trachea completely surrounding the tube, those of the 

 bronchi incomplete mesially. 



At the junction of the trachea with the bronchi occurs the 

 characteristic vocal organ, the syrinx (syr.), found in no other class. 

 The last three or four rings of the trachea (Fig. 1052, tr.), and the 

 first or bony half-ring of each bronchus (br.), are modified to form 

 a slightly dilated chamber, the tympanum, the mucous membrane 



