THORAX AND ABDOMEN OF THE HORSE 



165 



about 2 cm. This portion of the duct is known as the ampulla, but it 

 is to be noted that the increase in diameter is caused by a thickening 

 of the wall by glandular tissue, and not by any increase in the lumen of 

 the tube. Beyond the ampulla the duct narrows abruptly. 



The seminal vesicles (Vesiculte seminales). — These are pear- 

 shaped, hollow bodies partly enclosed in the urogenital fold lateral to 

 the ampullae of the deferent ducts and dorsal to the last part of the 

 ureters. Their dorsal surface is in contact with the rectum. The main 

 part, or body (corpus), of each vesicle expands towards a rounded cranial 



Left ureter. - 

 Round ligament. 

 Left ductus deferens. 



Lateral umbilical fold. -- 

 Urinary bladder. - 



Left seminal vesicle 



Left lobe of prostate. - 



Isthmus of prostate. 

 LIrethra. 



Left bulbourethral gland. 

 A. bulbi urethrae 



M. bulbocavernosus. 



Corpus cavernosus penis 

 (in section). 



- Right ureter. 



•Right ductus deferens. 



Urogenital fold. 



Right seminal vesicle, 

 ut edge of peritoneum. 



rostatic utricle, 

 prostaticus. 



M. urethralis. 



A—^— — M. ischiocavernosus. 



Fig. 73.— Dorsal view of the urinary bladder and intrapelvic urethra of the male, 

 with their associated structures. 



extremity, the fundus, while its caudal end, approaching the middle 

 line, narrows to an excretory duct (ductus excretorius) that opens into 

 the urethra underneath the prostate. 



It is often stated that the excretory duct of the seminal vesicle joins 

 the termination of the deferent duct of its own side in a common 

 ejaculatory duct (ductus ejaculatorius) ; but in most horses the two 

 ducts open into the urethra by a common orifice (orificium ejaculatorium) 

 or diverticulum. 



The PROSTATIC UTRICLE (Utriculus prostaticus). — When the dorsal 

 layer of the urogenital fold is removed, it is generally possible to find 



