THE PIGEON 



411 



into the distal limb of the duodenum, two about the 

 middle of its length and one, which is longer than the 

 others, near the end. There are two bile ducts, which 

 run from the large, bilobed liver and join the duodenum, 

 the wide left duct opening into the proximal limb and the 

 narrower right duct into the distal limb near the first two 

 pancreatic ducts. There is no gall bladder in the common 

 pigeon. The ileum is a much-coiled tube about two and a 

 half feet in length. The rectum is about an inch and 

 a half long. Its beginning is marked by a pair of small 

 rectal cceca ; behind it passes into 

 the cloaca. This has three regions 

 separated by shelves of the wall. 

 The first and largest is the copro- 

 daum into which the rectum opens, 

 the small middle division is the 

 urodczum into which the urinary and 

 generative ducts open, the third, of pf- 

 medium size, is the proctodeum ; upon 

 its dorsal surface there opens in the Fig. 301.— A diagram 

 young a glandular sac, the bursa matic section of the 

 Fabricii, of unknown function. 



The glottis, behind the root of 



the tongue, opens into ^., UpP e7reg;o„ of cloaca 

 5„p„„ "» the voiceless larynx, from into which rectum 

 ° g which the long trachea, ope ' ls: ? '" ;i = ' 



strengthened with bony rings, leads 

 back along the neck, lying at first 

 below the gullet and then at its left 

 side. At the base of the neck it 

 divides into the two bronchi; these run outwards and 

 backwards to the lungs, which lie against the dorsal walls 

 of the thorax covered with peritoneum below only. The 

 hinder end of the trachea is dilated and forms, with the 

 beginnings of the bronchi, the syrinx or organ of voice. 

 Sound is produced by the vibration of the membrana semi- 

 lunaris, a delicate vertical fold of mucous membrane 

 extending forwards from the angle between the bronchi. 

 The latter not only give off tubes which branch and form 

 the spongy lungs, but also pass right through these organs 

 and are connected with a system of large air sacs, of 



v-cL 



cloaca of a male 

 bird. — After 

 Gadow. 



region into which ureter 

 (».) and vas deferens 

 (vd.) open from each 

 side; pd., posterior 

 region into which bursa 

 Fabricii (B.F.) opens. 



