THE BLADDER. 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 wliich 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 inner 

 circularly, which enables it to yield to the pressm^e 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 fc>ecretion, to defend 



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