MUCOUS FOLLICLES OF THE URETHRA. 165 



urethra, in the lining membrane, are the openings of two ducts, 

 one on each side, that lead to small glandular bodies called 

 Cowper's glands, which are situated on each side of the urethra 

 below the bulb, but are covered by the acceleratores xirinae 

 muscles. 



The diameter of the urethra lessens after it leaves the prostate. 

 That portion of the canal which is between this gland and the 

 bulb, without investment, and therefore called the membranous 

 part, is the smallest in diameter. 



After it is invested with the spongy substance, it has a small 

 enlargement, and then continues nearly of one size, until it 

 arrives near the glans penis, when it again enlarges and alters" 

 its form, being no longer cylindrical, but flattened. Its broad 

 surfaces have now a lateral aspect. 



From the bulb of the corpus spongiosum to this last en- 

 largement, the appearance of the inner surface of the urethra 

 is uniform. The membrane is thin and delicate, and in a healthy 

 subject, who has been free from disease of these parts, is of a 

 whitish color; but blood-vessels are very perceptible in it. 

 When it is relaxed, it appears to be thrown into longitudinal 

 wrinkles ; but it admits of considerable extension ; being some- 

 what elastic : when extended, its surface appears smooth, as if 

 it were covered with an epithelium. Mr. Shaw, of London, 

 has described a set of vessels immediately below the internal 

 membrane of the urethra, which, when empty, are very similar 

 in appearance to muscular fibres. He says he has discovered 

 that these vessels form an internal spongy body, which passes 

 down to the membranous part of the urethra, and forms even 

 a small bulb there. His preparation with a quicksilver injec- 

 tion of the part is certainly a very satisfactory proof of its ex- 

 istence.* Throughout the whole extent of this part of the 

 urethra, are the orifices of a great many mucous ducts or 

 sinuses, which pass obliquely backwards. Many of these are 

 so small that they cannot be penetrated by a bristle, or probe 

 of that size ; but some are larger. It has not been observed 

 that any glandular body immediately surrounds them, although 

 they secrete the mucus with which the urethra is lubricated. 

 * See Med. Chirurg. Transactions of London, vol. x. 



