THORAX AND ABDOMEN OF THE HORSE 



163 



be raised, a flat bundle of pale fibres will be disclosed. They originate 

 from the first two coccygeal vertebrae, cross the lateral face of the 

 rectum close to the border of the external sphincter, and blend with 

 the corresponding fibres from the opposite side ventral to the anus. 

 From this point the fibres are continued on to the penis, where they 

 have already been traced to the neighbourhood of the glans. 



The urinary bladder (Vesica urinaria). — An ovoid sac, with a 

 strong muscular wall, the urinary bladder rests on the ventral wall of 

 the pelvis, and possibly also on the ventral wall of the abdomen. For 

 descriptive purposes, it is divided into a main portion or body (corpus 



Left seminal vesicle. 



Lateral umbilical fold. 



Left ureter. i 

 Round ligament. 



Left lobe of prostate. 



M. virethralis (in section). 



Left bulbo-urethral gland. 

 I A. bulbi urethrte. 



Left ductus defere 

 Middle umbilical fold. 



Line of peritoneal reflection 



M. bulbocavernosus. 



' Corpus cavernosum penis 



I (in cross section). 



Urethra. 



Urinary bladder. 



Fig. 72.— Lateral aspect of the urinary bladder and pelvic part of the urethra 



of the male. 



vesicae) ; a blunt cranial end, the vertex (vertex vesic*) ; and a narrow 

 neck (collum vesicae) continuous with the urethra. 



The neck lies on the internal obturator muscle medial to the obturator 

 foramen. The dorsal relations of the bladder are the prostate, the 

 urogenital fold and its contents (the terminations of the deferent ducts 

 and ureters, the seminal vesicles and the prostatic utricle) and the 

 rectum. On either side the bladder is related to the wall of the pelvis. 



Naturally the relations of the vertex depend in some measure upon 

 the amount of distension of the organ. It is not commonly the case 

 that the distension is so great as to carry the vertex to any considerable 

 distance beyond the margin of the pubis, and, consequently, this part of 

 the bladder is generally in contact with the pelvic flexure of the great 

 colon and the end of the left ventral colon. Coils of small intestine or 



