THE GENERATIVE APPARATUS OF BIRDS. 889 



majora ; the other mucous, the labia minora (or nymphx). The labia majora are 

 convex externally, continuous above with the mons Veneris, and unite below to form an 

 acute angle, named the fourcheUe ; they are covered externally with hair. The labia 

 minora, more or less developed, leave the Iburchette, and extend around the entrance to 

 the vagina, uniting above the clitoris, and forming the prepuce of that organ. 



The clitoris is lodged in the superior commissure of the vulva ; its point is directed 

 downwards, especially during erection; its base is attached, on each side, to the two 

 erectile lobes which constitute the bulb of the vagina (bulbi vestibuli). 



Two racemose glands, the vulva-vaginal or glands of Bartholine, pour their secretion 

 over the walls of the vestibule. 



Mammx. These are pectoral, and two in number. In their centre, they present an 

 enormous papilla -the nipple into which the excretory canals open ; it is surrounded by 

 a brown circle, the areola of the nipple. 



CHAPTER III. 



GENERATIVE APPARATUS OF BIRDS. 



1. Male Generative Organs. 



THE generative organs of the male are the testicles, and an excretory apparatus much 

 simpler than that of mammals. 



Testicles. These organs are placed in the sublumbar region of the abdominal cavity, 

 behind the lungs, and below the anterior extremity of the kidneys. Their form is 

 usually oval, and their volume varies with the different species, as well as at different 

 seasons ; at the breeding season they are greatly developed. 



Excretory Apparatus. In birds there is not, properly speaking, any epididymis. The 

 vas deferens passes from within the posterior extremity of the testicle, is directed in a 

 flexuous manner backwards, draws near to the ureter on its own side, going along the 

 kidney with it, and arriving at the cloaca, where it terminates by an orifice to be alluded 

 to hereafter. In the Duck, it has near its termination a small oval vesicle, .always filled 

 with spermatic fluid. 



Organ of Copulation. This varies with the species. In the Gallinacx, it is only 

 a small papilla placed below, near the margin of the cloacal opening, and between the 

 two orifices of the deferent canals. This papilla is traversed by a furrow through which 

 the semen flows. In the Palmipedes, this organ is much more developed, and is 

 peculiar. Contained within a tubular .cavity in the cloaca, it is protruded externally at 

 the moment of copulation by the eversion of this cavity, like a finger out of a glove ; it 

 then appears as a long pendant appendage, twisted like a cork-screw. 



2. Generative Organs of the Female. 



The development of the young animal taking place external to the female, the 

 generative organs are limited to that producing the ovum, and the duct through which it 

 passes on leaving the ovary. 



Ovary. In birds there" is only one ovary, which is situated on the left side, the right 

 one becoming atrophied very early in nearly all species. This ovary is situated, like the 

 testicles, in the sublumbar region of the abdominal cavity, and constitutes a more or less 

 voluminous body, composed of a variable number of ovules in process of development : 

 some very young, little, and white; others more advanced in age, being larger and 

 yellow in colour. The ova are enveloped in a very vascular cellular membrane, which, 

 when they are ripe, splits in a circular manner, following an equatorial line, and permits 

 the escape of the essential part of the egg the yellow (yelk), or vitellus. 



Oviduct. This duct is long, very wide and dilatable, and very flexuous. It begins, 

 near the ovary, by an unfringed pavilion, and terminates in the cloaca by a somewhat 

 narrow orifice, which is considerably widened when the egg passes through it. The egg, 

 composed, on entering the oviduct, of the fundamental part named the yelk, or vitellus, is 

 enveloped in an albuminous sphere during its progress towards the cloaca, and after- 

 wards with a protecting shell. The oviduct of birds is, therefore, something more than 

 an excretory canal, as it participates in the formation of the ovum. It is composed of 

 three membranes : an external, serous, maintains the tortuous tube ; a middle, muscular ; 

 and an internal, mucous. 



