THE BIADDKK. 
281 
THE BLADDER. 
PLATE IX. Fig. 2, k 
The bladder occupies the middle and lower portion of 
the pelvis. In its undistended condition it is wholly con¬ 
fined to the cavity of the pelvis; but when full, its fundus 
advances before the pubes into the abdomen, the advance¬ 
ment being in ratio with the degree of distention. It is 
pretty nearly pear-shaped. 
We have described how the urine is separated from the 
blood, when treating of the kidneys. The urine which is 
separated is discharged by these minute vessels into larger 
ones, which terminate in the kidney, which is termed its 
pelvis, and from thence led into the ureter duct, n } n , to the 
bladder, h, which we have represented distended with urine. 
The urine is constantly secreted and flows continually from 
the kidneys through the ureter ducts. It is this elastic 
property of the bladder which enables animals to retain the 
urine beyond the time which it is filled to its unstretched 
capacity, and prevents that constant flow which would be 
the result but for this beautiful provision. 
The bladder is provided with three coats. The outer 
one covers the greater portion of it, and is a part of the 
peritoneum; the muscular coat consists of two layers of 
fibres; the external running longitudinally, and the innei 
circularly, which enables it to yield to the pressure of the 
urine as the cavity fills, and again contract to a small size 
when emptied. This contractile property also assists in 
expelling the urine from the bladder. The inner or mucous 
coat is white, soft in its texture, and highly organized. It 
possesses numerous follicles, or little glands, from whose 
excretory pores issue a plentiful mucous secretion, to defend 
