242 ANATOMY OF THE ABDOMEN. 



with the hgamentum latum, it travels with it to the 

 upper part of the bladder ; and finally inserts itself at 

 some distance from the other within that viscus, piercing 

 the coats obliquely, and running between them for a short 

 distance ; this mode of entrance performing the office of a 

 genuine valve. 



THE BLADDER. 



This is a membranous and muscular sac of a pyriform 

 shape under distention, in which state it stretches beyond 

 the pubis, and may be then felt in the belly. It will con- 

 tain several quarts of urine, but is usually stimulated to 

 an early evacuation. It is surmounted by the rectum in 

 the horse, and the vagina in the mare. The bladder is 

 attached to the parietes of the pelvis by the peritoneum, 

 which forms its lateral ligaments ; the peritoneum being 

 superiorly reflected from the bladder over a part of male 

 rectum and female vagina. The bladder has three tunics : 

 the outer consists partly of peritoneum, which is to be seen 

 only over its fundus and part of its body ; the other portion 

 being covered by dense cellular tissue. The middle is the 

 muscular coat, whose fibres, longitudinal and oblique, adapt 

 it for uniform and complete contraction. The internal 

 lining membrane is villous, from the vascular surface of 

 which a mucus is secreted, to defend the organ from the 

 irritation of the urine. At its posterior part the bladder is 

 obliquely pierced by the ureters in the manner stated. 

 The neck of the bladder, which is surrounded by yellow 

 elastic tissue, terminates in the urethra. The arteries of 

 the bladder are derived from the minute branches given off" 

 by the internal iliacs ; its venal trunks return their blood 

 into the internal iliac veins ; and the nerves are given from 

 the sacral and abdominal plexuses. 



THE PHYSIOLOGY OF THE URINARY ORGANS. 



Urine may be considered as a separation from the blood 

 of its fluid part ; the separating office being effected by 

 the agency of the kidneys ; which organs therefore appear 

 united in function with the skin, and with the exhalant 

 bronchial surface, in aflfording outlets to the superfluity of 

 the vascular system. But of these three excretions, that 



