THE URINARY ORGANS. 79 



vessels Into a reservoir, called the pelvis, situated In the me- 

 dullary part of the kidney. From the pelvis of the kidney arises 

 a long white tube, called the ureter, which leaves the kidney at 

 its notch, and runs along the lumbar vertebrre to the pelvis of the 

 body, where it Is attached to the upper and lateral part of the 

 bladder, on which It continues its course towards the neck of the 

 bladder. Before it reaches the neck It disappears, by penetrating 

 the external coats of the bladder, passes a short distance, and 

 then terminates by piercing the internal coat in an oblique 

 direction. 



The kidneys are well supplied with nerves, which enter them 

 with the blood vessels. 



Near the kidneys are two small bodies, called the capsulas 

 renales, whose use is unknown. 



The BLADDER Is situated entirely within the cavity of the 

 pelvis, when In an undistended state; but when full, a portion of It 

 projects Into the abdomen. It is attached to the pelvis by cellular 

 membrane, but is chiefly kept In its situation by means of peri- 

 toneum, by which it is partially covered. It is i:)laced at the 

 lower part of the pelvis, having immediately above It the rectum 

 in the male, and the vagina in the female. The bladder is 

 usually distinguished into three parts : the fundus, the body, and 

 the cervix, or neck. The fundus is the round extremity, which 

 often projects Into the abdomen ; the body forms the principal 

 bulk of the bladder ; and the cervix Is the posterior narrow part, 

 which, however. Is thicker than the rest, and is united to the 

 urethra. 



The bladder is composed of three coats : the external, the In- 

 ternal, and the muscular. The former is formed by peritoneum, 

 and covers the anterior part of the bladder only. The internal 

 or mucous coat forms the principal thickness of the bladder, 

 and secretes a mucus for its internal lubrication, and to prevent 

 the irritating effects of the urine. This coat possesses much sen- 

 sibility, and is largely supplied with nerves. The muscular coat 

 is composed of two orders of fibres, longitudinal and circular ; 

 the former of which will diminish the length, and the latter the 

 breadth, and the united contraction of both will lessen the cavity 

 so as to expel the contents. 



The neck of the bladder Is more abundantly furnished with 

 circular fibres than the other parts, and their office in this situa- 

 tion is to prevent the urine from escaping by closing the cavity. 

 These fibres, when contracted from spasm, occasion a retention 

 of the urine. 



The urine Is discharged from the body through a membranous 

 canal, called the urethra, which, in the male. Is of considerable 

 length, extending from the bladder to the extremity of the penis. 



