TJie Pelvis. 271 



is the commencement of the urethra. The bladder is 

 supported by ligaments formed by the pelvic fascia and 

 the peritoneum, and is composed of three planes of mus- 

 cular tissue a longitudinal plane externally, a middle 

 one, of circular fibres, and an internal one, of somewhat 

 longitudinal arrangement. Externally, the muscular wall 

 of the bladder is covered, to some extent, by peritoneum, 

 while, internally, it is in contact with mucous membrane. 

 The mucous membrane is thrown into folds, except that 

 portion, which corresponds to the triangle at the base, 

 above referred to. This portion is called the trigone, and 

 it is almost an equilateral triangle, in shape, the angles be- 

 ing formed by the orifices of the ureters, behind, and by 

 the beginning of the urethra in front, and these angles 

 are about one and a half inches distant from each other. 

 In the region of the trigone, the mucous membrane is 

 paler, smoother and more firmly adherent to the subjacent 

 coat than it is elsewhere in the bladder. 



In the infant, at birth, the bladder is an abdominal or- 

 gan, having been crowded out of the pelvis because of the 

 narrowness of the latter, and has its anterior surface (un- 

 covered by peritoneum), resting against the abdominal 

 parietes. It is situated so high in the abdomen in infancy, 

 that the orifice of the urethra is on a level with the upper 

 border of the symphysis. It then begins to gradually sink 

 until about the ninth year, after which age it remains sta- 

 tionary until puberty, and, after that period, it slowly 

 sinks until it gains the position it normally occupies in the 

 adult. The bladder when empty is either contracted or 

 relaxed. In the former condition it is somewhat dome- 

 shaped, whereas, in the latter, the superior part rests on 

 the inferior part, like one saucer on another. Kelly, who 

 has devoted considerable study to cystoscopic examination 

 of the female bladder, states that the upper portion of the 



