474 MANUAL OF ZOOLOGY SECT. 



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. J-j). 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 cloaca : it atrophies in the adult. 



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 

 thy mus on each side of the neck. The adrenals (Fig. 273, 

 adr) are irregular yellow bodies placed at the anterior ends 

 of the kidneys. 



The /<?#/.$ (Fig. 270, gl) is situated just behind the root 

 of the tongue and leads into the larynx which is supported 

 by cartilages, but does not, as in other Vertebrates, 

 function as the organ of voice. From the larynx an elongated 

 tube, the trachea or wind-pipe, the wall of which is supported 

 by numerous bony rings, runs back along the ventral aspect 

 of the neck to enter the body-cavity, where it divides into 

 the right (r. br) and left bronchi, one passing to each of 

 the lungs. At the junction of the trachea with the bronchi 

 is found the characteristic vocal organ, the syrinx (syr\ 

 found in no other class. 



The lungs (Fig. 270, Ing) are very small in comparison 

 with the size of the Bird, and are but slightly distensible, 

 being solid spongy organs, not mere bags with sacculated walls 

 as in Amphibia and many Reptiles. Their dorsal surfaces fit 

 closely into the spaces between the ribs, and have no 

 peritoneal covering, their ventral faces are covered by a 

 strong sheet of fibrous tissue, the pulmonary aponeurosis or 

 pleura, a special development of the peritoneum. 



Each main bronchus gives off secondary bronchi, and 



