COLUMBA 125 



leads to the lungs. The gullet swells out into the crop at the 

 base of the neck. This is a thin- walled sac in which the food 

 is temporarily stored. The stomach is modified in that the 

 glands are restricted to an anterior chamber, the proventriculus. 

 Following on this is the gizzard, which has thick hard walls, 

 and in which the food is crushed up with the help of stones 

 and grit. The duodenum leads out from the gizzard, and 

 receives the three ducts from the pancreas, and the two bile- 

 ducts from the liver, which does not possess a special gall- 

 bladder. The intestine is coiled, and leads to the rectum, 

 which bears a pair of cceca. The rectum leads to the cloaca 

 which is peculiar in that it is subdivided into three regions. 

 That into which the rectum opens is called the coprodaeum ; 

 next comes the urodaeum, into which the ureter and genital 

 ducts lead ; and lastly the proctodeum which opens to the 

 exterior. Into the proctodeum opens the bursa Fabricii, a 

 blind sac-like organ of unknown significance. 



Ccelom. — A knowledge of the relations of the ccelom is 

 necessary for a proper understanding of several of the organs 

 in birds. As in the lizard, the lungs are contained in folds of 

 the ccelomic epithelium which connect with the liver (forming 

 pulmo-hepatic ligaments), but in addition, these ligaments 

 make a connexion with the side wall of the general ccelomic 

 cavity. In so doing, they slant downwards and laterally from 

 the roof of the ccelomic cavity, and are called the oblique septa. 

 They separate a portion of the ccelomic cavity on their upper 

 and outer sides, from the remainder of the perivisceral ccelomic 

 cavity, forming the pleural cavities. Into these cavities the 

 lungs project. The gizzard is connected with the floor of the 

 ccelomic cavity by a post-hepatic septum, so that altogether the 

 cavity of the ccelom is considerably obstructed and divided up. 

 The pericardium is, of course, separated off from the rest of 

 the ccelom by the transverse septum, but it is important to 

 notice that in birds there is no diaphragm (see Fig. 126). 



Respiratory System. — The glottis leads into a long trachea 

 or windpipe, strengthened by cartilaginous and bony rings. 

 This trachea divides into the two bronchi, and at the point of 

 division a membrane extends forwards and projects into the 



