612 



BIRDS. 



cloaca. The predominance of urates in the active birds, with high 

 oxidation and blood very rich in red corpuscles should be borne in 

 mind when the physiological relations of uric acid to metabolism are 

 studied. 



In front of each kidney, at the base of the iliac vein, there lies a supra- 

 renal body. 



Reproductive System. 



The testes lie in front of the kidneys. They increase in 

 size before the breeding season. The sexual period in birds 

 is often narrowly limited. 



The spermatozoa pass from the testis into a vas deferens, 

 which lies to the outside of the corresponding ureter. The 



FIG. 216. Urinogenital organs of Pigeon. 



K., kidney; /., ureter; cl., cloaca; 7\, Testis; v.d., vas de- 

 ferens ; v.s., seminal vesicle ; ov., ovary ; od., oviduct ; r.r.od., 

 rudimentary right oviduct ; f.t., funnel at end of oviduct. 



vasa deferentia, slightly convoluted when full of sperms, 

 open separately into the median compartment of the cloaca. 



In the adult pigeon, and in most birds, there is only one 

 ovary ; that of the right side atrophies very early in life. 

 The right oviduct is represented by a small rudiment close 

 to the cloaca. 



The ovary is covered with follicles containing ova at 

 various stages of ripeness. As these ova become dilated 

 with yolk and otherwise mature they burst from the ovary, 



