726 



AVES. 



the same point as the other two, issues from the opposite extremity of 

 the pancreas, and enters the middle of the duodenum at the place where 

 the gut turns upon itself. 



Fig. 359. 



Digestive apparatus of a Fowl. 



(2059.) The spleen (fig. 359,/) is of very small size in aU birds ; it 

 is situated near the anterior extremity of the pancreas, and is loosely 

 connected to the side of the proven triculus (6). The distribution of its 

 vessels and its general structure are the same as in Mammalia. 



(2060.) The lymphatic system is well developed ; and the course of 

 the lymphatic vessels has been investigated with great care by various 

 anatomists. The vessels themselves are thin, and have but few valves ; 

 they principally accompany the larger blood-vessels from all parts of 

 the body to the aorta, around which they form a plexus, and ultimately 

 join to give rise to two principal trunks or thoracic ducts; these termi- 

 nate severally in the right and left jugular veins, and into these vessels 

 the greater proportion of the lymph and chyle absorbed is of course 

 poured, to be mixed with the circulating blood. 



(2061.) Before describing the circulatory apparatus of Birds, it will 

 be advisable in the next place to consider the nature and disposition of 

 their organs of respiration, which, from what has been already stated 



