1254 



URETHRA. 



elephant ; they have a similar structure as the 

 prostate, but are comparatively larger ; they 

 are reddish in colour, very irregular exter- 

 nally, and present a lobular appearance. They 

 are divided into two portions ; a smaller, near 

 the bulb, and another large portion. In the 

 centre of the first there is a considerable 

 cavity, which receives the fluid poured into it 

 by smaller cavities, and these communicate 

 with still smaller cellules. From the prin- 

 cipal cavity a canal arises, which, communicat- 

 ing with that of the other portion of the 

 gland, forms a single common canal. The ex- 

 cretory duct is formed of two branches ; it 

 passes a short distance in the walls of the 

 urethra, before it opens into the bulb. The 

 glands are covered by a thick muscular layer, 

 the fibres of which converge to a tendon, 

 which is fixed to each corpus cavernosurn. 



In the wild boar the gland is elongated and 

 cylindrical, formed of a firm substance com- 

 posed of minute cells, which uniting form 

 larger cells, and these communicate with a 

 common central cavity, from which an excre- 

 tory duct arises ; this opens on the side of a 

 cul-de-sac in the commencement of the bulb 

 of the urethra. They are each completely 

 surrounded by a muscle. In Solipeds they 

 form an oval swelling on each side of the 

 pelvic portion of the urethra. They are sur- 

 rounded by muscular and tendinous fibres : 

 each opens by a dozen orifices, ranged in 

 rows, into the adjacent part of the urethra. 



Amongst the Ruminants, in the chamois, they 

 are of the shape and size of a pigeon's egg ; 

 its canal terminates in the usual situation. They 

 are similar in all ruminants where they exist. 



Amongst the Marsupialia they are remark- 

 able for their number : thus, there are as many 

 as six in the Mexican opossum, phalangers, 

 phascolymus, and giant kangaroo ; four in the 

 sarigue and kangaroo-rat. In the giant kan- 

 garoo two are placed, one by the side of the 

 other, over the urethra, just behind the crura 

 penis ; two others are situated on each side 

 behind the crura, and are larger than the 

 others. They are all invested by a muscular 

 and aponeurotic envelope, and are composed 

 of canals passing lengthways : they resemble 

 in structure the prostate. 



In the echidna and ornithorynchus, amongst 

 the Monotremata, there is a gland on each 

 side of the cloaca, small, and of an oval 

 shape, containing within it a central canal 

 opening into an excretory duct: this pene- 

 trates the constrictor cloacae, and joins a small 

 seminal canal detached from the urethra, near 

 its termination in the cloaca. The gland is 

 surrounded by a thick muscle, the action of 

 which is forcibly to throw forwards the fluid 

 along the long excretory canal with which it 

 is provided. 



Cowper's glands are altogether wanting in 

 birds. They are not found in reptiles gene- 

 rally ; but in the amphibious Urodeles the 

 genito-urinary opening is surrounded by a 

 glandular apparatus in some respects ana- 

 logous. In fishes they are wanting. 



They belong to the class of glands desig- 

 nated by Cuvier as supplementary to the 

 male organs of generation, and their use is 

 to pour out a fluid to lubricate the spongy 

 portion of the urethra, and by blending with 

 the seminal and other fluids, to assist in the 

 general distension of the canal. 



Bloodvessels of the Urethra. The urethra 

 is a highly vascular membrane, and its 

 arteries are derived on either side from 

 that branch of the pudic which enters 

 the corpus spongiosum at the bulb, and is 

 known by the name of the arteria corporis 

 spongiosi urethrce vel arteria bidbi. This artery 

 divides into small branches, many of which 

 are distributed on the cells of the corpus 

 spongiosum, whilst others pass through this 

 body, and penetrating the elastic tunic of the 

 urethra are distributed upon its mucous sur- 

 face, forming intricate plexuses between and 

 at the basis of its columns : others are des- 

 tined to the lacuna? over which they form a 

 delicate network, which conveys to these 

 crypts a cellular appearance. They all freely 

 anastomose on the general surface of the 

 urethra, and at the meatus communicate with 

 those minute branches of the arteria dorsalis 

 penis, which, having reached the prepuce, are 

 reflected over the cutaneous surface of the 

 glans penis. 



The veins either communicate with those 

 of the spongy body, and empty themselves 

 into the dorsal vein of the penis, or terminate 

 at once in the prostatic plexus by means of 

 those already described in the membranous 

 portion. 



Nerves. The nerves are exceedingly 

 small ; they accompany the arteries of the 

 bulb, but cannot be traced into the urethral 

 membrane, although the high sensibility of 

 this structure even in health, and especially 

 under disease, indicates at once a considerable 

 nervous supply. The nerves are derived 

 partly from the pudic nerves, which give 

 minute branches, taking the course of the 

 arteries of the bulb, and partly from the 

 plexus situated beneath the neck of the blad- 

 der formed by some small branches of the 

 sacral nerves and sacral ganglion of the sym- 

 pathetic. 



The lymphatics join the superficial and 

 deep lymphatics of the penis, and either ter- 

 minate in the inguinal glands, or, passing into 

 the pelvis with the pudic vessels, join the 

 ganglion situated around the internal iliac 

 artery. 



Function. The office of the urethra is 

 to give exit to the urine from the bladder, and 

 the secretions of the testes and their ap- 

 pendages the vesiculae seminales, the prostate 

 and Cowper's glands. For the free discharge 

 of the urine, the urethra is in a passive con- 

 dition, and the penis relaxed, and as free as 

 possible of blood ; the muscles surrounding 

 the membranous portion together with the 

 slightly resisting urethra yield to the efforts 

 of the detrusor urina?, and the urine passes 

 in a stream varying in size and force ac- 



