178 EQUINE ANATOMY. 



sion. Modes of attachment : the meso-reetmn, a fold 

 of the colic mesentery, a fold of the peritoneum, the 

 suspensory ligaments of the penis and a triangular 

 fasciculus of muscular fibres, a prolongation of its 

 fleshy coat. Structure : a serous membrane, a fleshy 

 coat of longitudinal and annular fibres, a mucous mem- 

 brane with transverse and longitudinal folds ; arteries 

 from the small mesenteric and internal pudic ; nerves 

 from the pelvic or hypogastric plexus. 



Anus. — The posterior opening of the digestive ca- 

 nal, pierced at the posterior extremity of the rectum 

 under the base of the tail. Structure : mucous mem- 

 brane of the rectum, muscular fibres of the rectum 

 forming an internal sphincter, an external sphincter, 

 a retractor or ischio-anal muscle and the skin, fine 

 and very adhering to the muscular tissue underneath. 



Bladder — Form : ovoid with a large extremity or 

 rounded cul de sac turned forward, and a posterior 

 extremity, the neck, continued hy the urethra. Its 

 average weight is about sixteen ounces. Modes of at- 

 tachment : a fold of the peritoneum forming the three 

 liofaments of the bladder. Its interior shows the vesi- 

 cal trigone. Structure: a mucous membrane intern- 

 ally, a muscular coat, longitudinal, circular, oblique and 

 spiroid fibres, and a serous coat in its anterior region ; 

 arteries from the vesico-prostratic ; nerves from the 



