168 LENGTH OF THE URETHRA. 



Thus constructed, of the corpora cavernosa and the urethra 

 with its corpus spongiosum, and attached to the pelvis as above 

 mentioned, the penis is invested with its integuments in the fol- 

 lowing manner. 



The entire length of the urethral canal from its commence- 

 ment at the back part of the prostate gland that is at the neck 

 of the bladder, to its external orifice in the glans penis, varies 

 in different subjects when distended or gently drawn out, from 

 eight to ten inches. The difference in length in different indi- 

 viduals is found to depend upon the greater or less development 

 of the penis from the bulb of the urethra outwards ; the length 

 of the membranous and prostatic portions being nearly the same 

 in all adult subjects. The membranous portion of the urethra 

 extends from the bulb to the anterior -margin of the prostate, and 

 is about three quarters of an inch long; it is rather longer on its 

 upper than its lower surface, in consequence of the extension of 

 the pendulous portion of the bulb backwards. In place of the 

 spongy portion, it is covered on its outer surface with a thin 

 layer of pale cellulo-muscular fibres like that forming the neck of 

 the bladder (see page 131,) with which it is continuous.* 



* Mr. James Wilson described a muscle, designated commonly as the muscle 

 of Wilson, (see vol. 1, p. 338,) situated one upon each side of the membranous 

 portion of the urethra, called the musculus compressor urethras or pubo-urethra- 

 lis. It is oblong, quadrilateral, and flattened from without inwards. It arises 

 from a short tendon on the back part of the pubis, near the symphysis. It in- 

 creases in size as it descends, embraces closely the membranous portion of the 

 urethra, and at the lower surface of the latter is closely connected with its fellow 

 of the opposite side, so that the two form as it were a muscular ring around 

 the urethra. In front it is usually connected with the posterior part of the 

 accelerator urinae muscle, and below it is connected to the levator ani. It ap- 

 pears to me to form a part of the latter muscle, and to act as a constrictor of 

 the urethra to the male and of the vagina in the female. A transverse fasciculus 

 belonging to this muscle was pointed out by Santorini to which the attention of 

 the profession has recently been called by Mr. Guthrie. Among English anato- 

 mists it is now known as the muscle of Guthrie. It arises on each side from 

 the eras ischii, and is inserted into the under part of the membranous portion 

 of the urethra, the perineal centre, and the point of the prostate. It embraces 

 Cowper's glands, and is connected with the lower part of Wilson's muscle. 

 These are voluntary muscles, according to Mtlller, and are the principal agents 

 by which we exercise any voluntary control over the discharge of urine. When 

 spasmodically contracted, they compress the urethra, and often render the pass- 

 ing of a catheter along this portion of the canal impossible, till the spasm is 

 relaxed by medicinal means. p. 



