3i8 GENERAL ORNITHOLOGY part ii 



emulsionising fat. The liwr is a well-known glandular organ of 

 very special structure and function, secreting the fluid called Vile, 

 also received into the intestine. It is of moderate size in birds, 

 and deeply divided into two principal (right and left) lobes : in 

 some birds there is also a smaller lobe ; and one of the large lobes 

 may also be divided. The lobes dispart above to receive between 

 them the apex of the heart ; they are held in place by pleuro- 

 peritoneal folds contributing to form the thoracic-abdominal air-cells. 

 This viscus receives venous blood from the extensive portal system ; 

 two hepatic veins then conduct it to the post-caval. The emunctory 

 ducts, carrying off the bile, are two or three in number. One at 

 least goes directly to the intestine, and another to the gall-bladder, 

 when that cyst exists ; in which case there is a separate cystic duct 

 from the bladder to the intestine, no ductus communis choledochus, or 

 duct common to the hepatic substance and its cyst, being formed 

 in birds. Two hepatic ducts may coexist with a cystic duct, 

 making three to the intestine, all separate ; two is the rule when 

 there is no gall-bladder. These emunctories commonly enter the 

 intestine some distance apart, and beyond the pancreatic ducts. The 

 gall-bladder is generally present, sometimes absent ; it may occur 

 or not in closely related genera of birds. 



g. Oology : the Urogenital Organs 



The Urinary and Generative Org-ans may be conveniently con- 

 sidered together, not only on account of their close anatomical 

 relations, but because their physiological functions, totally diverse 

 in adult life, are primitively related in the most intimate manner. 

 For it is a singular fact that the mean office of straining urine out 

 of the system is at first sustained by a structure (Wolffian body), in 

 closest connection with which, in the female, actuall}^ as a part of 

 which, in the male, are later developed those organs (ovary and 

 testis) whose exalted office is creative ; for these permanent genital 

 glands procreate the microscopic creatures called Dijnamcmuvhce, the 

 marriage of which results in the reproduction of a complex 

 organism like the male or female parent. (See Figs. 103, 104, and 

 following.) 



The Wolffian Bodies, or 'primordial kidneys, are a pair of tuluilar 

 structures which appear very early in the progress of development 

 of the embryo, beneath the spinal column, in front of the fore end 

 of the future kidneys ; with each of them is developed a duct, the 

 JFoIffian duct, which carries their excretion into the cavity of the 

 allantois (the future cloaca). Upon the appearance of the true 

 kidneys, the transitory Wolffian bodies and ducts lose their urinary 

 function ; they ultimately disappear from the female, for the most 



