538 



URETHRA. 



posed of two layers, a mucous coat and an elastic fibrous coat. The mu 

 cons coat is thin and smooth ; it is continuous, internally, with the mucous 

 membrane of the bladder ; externally, with the investing membrane of the 

 glans ; and at certain points of its extent, with the lining membrane of the 

 numerous ducts which open into the urethra, namely, those of Cowper's 



Fig. 236 



glands, the prostate gland, vasa deferentia, and vesiculse seminales. The 

 elastic fibrous coat varies in thickness in the different parts of the course 

 of the urethra: it is thick in the prostate gland, forms a firm investment 

 for the membranous portion of the canal, and is thin in the spongy portion, 

 where it serves as a bond of connexion between the mucous membrane 

 and the corpus spongiosum. The urethra is about nine inches in length, 

 and is divided into a prostatic, membranous, and spongy portion. 



The Prostatic portion, a little more than an inch in length, is situated 

 in the prostate gland, about one-third nearer its upper than its lower 

 surface, and extending from its base to its apex. Upon its lower circum- 



* A longitudinal section of the bladder, prostate gland, and penis, showing the urethra. 

 1. The urachus attached to the upper part of the fundus of the bladder. 2. The recto- 

 vesical fold of peritoneum, at its point of reflexion from the base of the bladder, upon 

 the anterior surface of the rectum. 3. The opening of the right ureter. 4. A slight 

 ridge, formed by the muscle of the ureter, and extending from the termination of the 

 ureter to the commencement of the urethra. This ridge forms the lateral boundary of 

 the trigonum vesicse. 5. The commencement of the urethra; the elevation of mucous 

 membrane immediately below the number is the uvula vesicae. The constriction of the 

 bladder at this point is the neck of the bladder. 6. The prostatic portion of the urethra. 

 7. The prostate gland ; the difference of thickness of the gland, above and below the 

 urethra, is shown. 8. The isthmus, or third lobe of the prostate; immediately beneath 

 which the ejaculatory duct is seen passing. 9. The right vesicula serninalis ; the vas 

 deferens is seen to be cut short off, close to its junction with the ejaculatory duct. 10. 

 The membranous portion of the urethra. 11. Cowper's gland of the ri^ht side, with its 

 duct. 12. The bulbous portion of the urethra; throughout the whole length of the ure- 

 thra of the corpus spongiosum, numerous lacuna? are seen. 13. The fossa navicularis. 

 14. The corpus cavernosum, cut somewhat obliquely to the right side, near its lower 

 part. The character of the venous cellular texture is well shown. 15. The right crus 

 penis. 16. Near the upper part of the corpus cavernosum, the section has fallen a little 

 f .o the left of the middle line; a portion of the septum pectiniforme is consequently 

 seen. This figure also indicates the thickness of the fibrous investment of the corpus 

 cavernosum, and its abrupt termination at the base of (17) the glans penis. 8. The 

 'ower segment of the glans. 19. The meatus urinarius. 20. The corpus spongiosum. 

 VI The bulb of the- corpus spongiosum. 



