2i2 OUTLINES OF EQUINE ANATOMY. 



into it in the peculiar manner already described. Tlie 

 organ presents tiuo coats — muscular arid mucous. When it 

 is distended, the mucons coat may he seen between the mus- 

 cular fibres, which seem to be irregiilarly arranged, but they 

 present a species of oblique arrangement on closer inspec- 

 tion, forming what is termed detrusor urinw, while towards 

 the neck of the bladder they tend to assume the circular 

 form, producing the sphincter vesicce. The mucous coat 

 lines the bladder throughout, and is continuous with that 

 of the ureters, and with that of the urethra ; it presents- 

 thick and viscid epithelium, which serves to protect the 

 organ from the irritant action of the urine, and much of 

 which is expelled with that fluid. 



The urethra is a membranous elongated passage, com- 

 mencing at the neck of the bladder and running in a 

 backward direction as far as the ischial arch, around which 

 it winds, and then runs in a forward direction forming the 

 central part of the penis, to between the symphysis pubis 

 and the umbilicus. It consists of a mucous membrane, 

 which extends throughout, and in some parts presents large 

 mucous crijpts or lacunoe, which also communicates with 

 that hning the bladder, ejaculatory ducts, prostatic, and 

 Cowper's ducts, and with the lining layer of the prepuce. 

 It is divided into three ^ovtiows,, prostatic, membranous, and 

 spongy. The prostatic portion is the shortest, and is sur- 

 rounded by the prostate gland. It commences at the neck 

 of the bladder and passes to the membranous portion. 

 Its mucous membrane presents at its upper part two pecu- 

 liar prominences perforated by two foramina, the openings 

 of the ejaculatory ducts formed by union of the vasa 

 deferentia and of the ducts from the vesiculae seminales. 

 This prominence is the veru montanum or caput cjallina- 

 ginis. On either side also may be seen a row of small 

 papillae, on to which open the prostatic ducts. The mem- 

 branous portion extends from the prostatic as far back- 

 wards as the ischial arch, and on its postero-lateral parts 

 are two rounded bodies about the size of a walnut. These 

 are Coivpers glands, and like this jDortion of the canal 

 they are invested by a portion of muscle, Wilson's muscle, 

 the fibres of which run transversely above the canal from 

 one side to the other. Like the prostatic their ducts oj)en 

 upon numerous small papillse arranged in rows, one on 

 each side of this portion of the urethral canal. The 



