URETERS BLADDER URETHRA. 7 



The ureters are two membranous tubes leading from the 

 pelvis of the kidney to the bladder. They are external to 

 the peritoneum, and pursue a rather oblique course inwards 

 and backwards, entering the base of the bladder; they pass 

 for a certain distance between the muscular and mucous coats 

 of the bladder before perforating the latter. When the 

 bladder is being emptied, the muscular fibres contracting, by 

 the above arrangement, close effectually the open mouths of 

 the ureters, and prevent any reflux of urine into them. 



The bladder is lodged in the pelvic cavity, which it fills 

 more or less completely, according to the amount of urine 

 which it contains. When the urine is prevented by any 

 cause (as from stricture of the urethra) from escaping, the 

 bladder may become enormously distended. The bladder is 

 composed of an external muscular and an internal mucous 

 coat. It is perforated by three openings, viz., by the two 

 ureters, and by the orifice of the urethra, the canal destined 

 to convey the urine out of the body. 



The urethra. The organs belonging to the urinary sys- 

 tem, which I have described, are almost precisely alike in the 

 different domestic animals. The canal of the urethra is, how- 

 ever, modified not only in different species, but in the two 

 sexes. In the male it fulfils a double function, conveying the 

 spermatic fluid as well as the urine, whereas in the female it 

 does not form an integral portion of the generative system, 

 however intimately it is connected with it.* 



* A complete description of the male urethra involves an account of 

 the form and structure of the penis in different animals, and will be 

 more properly considered under the Organs of reproduction, as the 

 modifications which it undergoes seem more especially to have reference 

 to its function as a generative than a urinary organ. I shall therefore 

 in this place only touch upon the anatomy of the penis in so far as a 

 knowledge of it will enable us to understand the physiology of the 

 urinary organs. 



