166 TOPOGRAPHICAL ANATOMY OF THE 



au elongated, pyriform, blind tube occupying the middle line between 

 the two deferent ducts. This is the homologue of the uterus and vagina 

 of the female, and is consequently sometimes known as the uterus 

 niasculinus. The tube varies greatly in its degree of development, 

 and is sometimes impossible of demonstration. In other animals, on 

 the contrary, it is some 10 cm. in length, and may terminate cranially 

 in two very slender cornua. The utricle may open into the urethra, 

 or its caudal end may be blind. 



The urethra (Urethra). — The male urethra ^ (urethra masculina) 

 is a tube concerned in the transmission of both urine and semen ; con- 

 sec^uently it is sometimes designated the male urogenital canal. It 

 extends from the neck of the urinary bladder to the free end of the 

 penis, and is therefore divisible into pelvic and penile or extra-pelvic 

 portions. The pelvic part (pars pelvina), from 10 to 15 cm. in length, 

 runs along the ventral wall of the pelvis beneath the rectum. A por- 

 tion of it, the pars prostatica, is associated with the prostate and is not 

 so wide as that part which extends from the prostate to near the sciatic 

 arch. The thin urethral muscle (m. urethralis) covers the pelvic part 

 of urethra. The term isthmus urethrce is applied to the somewhat 

 constricted part of the tube that is related to the bulbo-urethral glands. 



The penile portion (pars cavernosa) of the urethra has already been 

 examined in connection with the penis (page 78). An examination of 

 the interior of the tube should be postponed. 



The bulbo-urethral glands (glandule bulbourethrales). — A short 

 distance from the sciatic arch an elongated or ovoid bulbo-urethral gland 

 lies on each side of the urethra covered by the urethral muscle. The 

 size of the glands varies in different animals ; but in the uncastrated 

 male their long diameter is approximately 4 cm., while the transverse 

 diameter is rather more than half the length. In the castrated animal 

 they are much smaller than thi.s. On section each gland consists of ill- 

 defined lobules separated by trabeculse, into the larger of which fibres 

 are projected from the urethral muscle. It will be observed later that 

 each gland pours its secretion into the urethra by several (5 to 8) 

 small excretory ducts (ductus excretoria). 



M. URETHRALIS. — The urethral muscle consists of dorsal and ventral 

 strata of transverse (and longitudinal) fibres, investing the dorsal and 

 ventral surfaces of the pelvic portion of the urethra. Some of the fibres 

 cover the surface of the prostate (m. prostaticus), while others, in like 

 manner, are associated with the bulbo-urethral glands. 



1 ovpriOpa (ourethra) [Gr.], urinary canal (ovpilw (oureo) to make water). 



