178 ANATOMY OF THE DOMESTIC FOWL 



grow, the seminal tubules become larger, and the amount of con- 

 nective tissue correspondingly less. 



In addition to the tubules, the spermatogenic cells, and the 

 connective tissue, there is also in the testicles more or less fat. 

 There is a small amount of connective tissue between the semi- 

 niferous tubules, in which locations there are also clusters of poly- 

 hedral cells, with round nuclei, others are the interstitial cells. 



The Vas Deferens (Fig. 54, D). Location and Shape. — Extending 

 from the epididjmius, is the vas deferens which runs backward 

 on the infero-intemal surface of the kidney and to the outside of 

 the ureter. It is very tortuous passing on the infero-lateral surface 

 of the kidney in company with the ureter and becoming somewhat 

 expanded posteriorly it terminates in the upper wall of the cloaca 

 in a rather small papiUa located in the uro-genital portion of the 

 cloaca anterior to the mouth of the ureter. This papiUa is the 

 organ of copulation and in ducks is very large, and spirally elongated, 

 and retractile forming a kind of penis. The papiUa is traversed 

 by a furrow on the upper surface through which the semen flows. 



Structure.— The vas deferens is covered and supported by the 

 peritoneum. Its wall is made up of a fibrous structure in which 

 may be found smooth muscle fibers. The wall does not possess 

 glands. It is lined with columnar epithehum. The posterior 

 end is expanded and terminates into a papilla. The base of the 

 papiUa is surroimded by a plexus of arteries and veins, which serve 

 as an erectile organ during the venereal orgasm, when the fossa 

 of the turgid papiUa is everted, and the semen brought into contact 

 with the similarly everted orifice of the oviduct of the female, 

 along which the spermatozoa pass by undulatory movements of 

 their ciUary appendage, or tail. 



THE FEMALE GENERATIVE ORGANS (Fig. 56) 



The female generative organs consist of one ovary and an oviduct. 



Location. — The ovary is located similarly to the testicles of the 

 male bird, in the sublumbar region of the abdominal cavity, just 

 at the anterior end of the kidneys, posterior to the lungs, and sKghtly 

 to the left of the center. 



Shape. — In the puUet the ovarian mass appears somewhat like a 

 bunch of grapes, being made up of from 3500 to 4500 smaU, whitish 

 spheres, which represent the undeveloped ova, and which in the 



