THE ANATOMY OF THE RUFFED GROUSE 



739 



and then forms several loops, the last one extending ventrad and at right angles to the axis 

 of the body. It then passes dorsad and anteriorly to join the large intestine. The two caeca 

 diverge at this point and form a series of coils at right angles to the body axis, posterior of the 

 gizzard. The small and large intestines are of equal diameter. There is considerable varia- 

 tion in the details of the arrangement of these structures. The Galli are grouped among the 

 birds with long caeca as opposed to the types in which they are small or functionless^". 



The large intestine (figure 81) is the shortest section of the gut. It lies just under the roof 

 of the visceral cavity and is divided into three parts, coprodeum, urodeum and proctodeum^. 



C/JRCTAe 



EPioEQtnia 



PaocTooLOAt 



FIGURE 81. LONGITIDINAL SECTION OF LARGE INTESTINE Ix 0.21 I 



The coprodeum extends from the caeca to the small flap which separates it fnmi tlx- urodeum. 

 The latter is a short section, bounded posteriorly by a flap. It receives the ureters as well as 

 the oviduct or the vasa deferentia. The proctodeum is the terminal section. On its dorsal side 

 is a diverticulum, the bursa Fabricii*. The external opening is smaller than the cavity of the 

 proctodeum. 



TABU'; 100. AVKRAGE MEASUREMENTS OF DIGESTIVE TRACT OF U. XDILT (JROUSE 



Urogenital System. The urogenital system is extremely uniform throughout the Class Aves 

 and is composed of the sex organs and their ducts, and the excretory organs. The kidneys 

 are paired structures lying ventral to the sacrum and dorsal to the aorta and its large 

 branches, the ischiadic arteries. Each kidney is lobed and sends the excretory products to 

 the cloaca through the ureter. 



* This is a sac-like pouch which is present in birds of the year np to an age of about nine months. It is therefore the 

 most reliable means of separating young from old birds up until alioul March 1. During the latter part of this period 

 it becomes progressively smaller and finally disappears, although it persists later in some individuals than in others. 



