360 



THE ANATOMY OF THE HORSE. 



Structure of the Urethra. The spongy portion has been described 

 with the penis. The prostatic and membranous portions have a mucous 

 lining, external to which is a muscular coat of non-striped fibres. 

 Observe the following points in connection with the interior of the 

 intra-pelvic part of the urethra (Fig. 50). On 

 the middle line of the roof of the tube, close 

 behind the communication with the bladder, 

 there is a mucous eminence — the colliculus 

 seminalis, or verumontanum. In the gelding this 

 is often small, and sometimes hardly recognis- 

 able, but in the stallion it is sometimes a con- 

 siderable eminence, like the tip of the little 

 finger. At each side of this projection is the 

 orifice of the ejaculatory duct. These orifices 

 in the stallion are sufficiently large to permit of 

 the tip of the little finger being insinuated into 

 them. This should be remembered, as the 

 point of catheter, if not guided along the floor 

 of the urethra, might easily pass into one of 

 them. At the summit of the colliculus, and 

 therefore on the middle line, is a very minute 

 opening — the orifice of the uterus masculinus. 

 Insert a fine bristle into it, and guide it on into 

 the tube. On the wall of the urethra at each 

 side of the colliculus, observe an irregular series 

 of minute orifices which belong to the ducts of 

 the prostate gland. Behind these on each side, 

 notice another series of small openings with a 

 linear arrangement. These are the orifices of 

 the ducts of Cowper's glands. Insert bristles 

 into a few of each set of openings, and guide 

 them on into the respective glands. Close to 

 the neck of the bladder the epithelium of the 

 urethra is of the same character as in the 

 bladder, but behind that point it is simple and 

 columnar. 



Structure of the Vesiculte Seminales. The 



walls of these are composed of fibrous, fibro- 



muscular, and mucous layers ; and contain many 



tubular glands, which discharge their secretion 



into the cavity, where it mixes with the semen. The bulbous portion 



of each vans deferens has the same structure. 



Directions. — The student must now return to the pelvis, at the roof 

 of which he is to dissect the lumbosacral plexus of nerves, and the 



Fig. 50. 



Bladder and Intrapelvic 

 portion of Urethra 

 opened from below 

 (Leyh). 



1. Vas deferens; 1'. Bulbous 

 part of the same ; 2. Douglass's 

 fold, joining the vasa defer- 

 entia ; 3. Bladder ; 4. Vesi- 

 cula seminalis ; 5. Orifices of 

 ureters ; 6. Prostate ; 7. Veru- 

 montanum with orifices of 

 ejaculatory ducts; 8. Orifice 

 of prostatic vesicle ; 9. Cow- 

 per's gland ; 10. Orifices of 

 ducts of prostate ; 11. Orifices 

 of ducts of Cowper's gland ; 

 12. Corpus cavernosum ; 13. 

 Corpus spongiosum with ure- 

 thra in its centre. 



