180 EXCEETION. 



peritoneum, covering the posterior portion completely, from 

 the openings of the ureters to the summit, about one-third 

 of the lateral portion, and a small part of the anterior portion. 



The middle, or muscular coat, consists of fibres of the 

 non-striated or involuntary variety, arranged in three toler- 

 ably distinct layers. 



The external muscular layer is composed of longitudinal 

 fibres, which arise from parts adjacent to the neck, and pass 

 anteriorly, posteriorly, and laterally over the organ, so that 

 when they are contracted they diminish its capacity chiefly 

 by shortening its vertical diameter. The anterior fibres of 

 this layer arise from the body of the pubis and the symphy- 

 sis by tendinous bands, known to most anatomists as the 

 anterior ligaments. These tendinous fibres spread out on 

 the prostate and are attached to its anterior surface. As 

 the fibres on the anterior surface pass over the summit of 

 the bladder, they interlace, and some of them are continuous 

 with the fibres coming from the posterior surface. The 

 posterior fibres arise from the base of the prostate, and, after 

 forming a distinct band an inch or an inch and a quarter in 

 breadth, spread out on the posterior surface of the bladder. 

 The lateral fibres arise from the sides of the prostate and 

 spread out upon the lateral surfaces of the bladder. In the 

 female, the posterior fibres arise ^from the dense fibrous 

 membrane between the neck of the bladder and the vagina, 

 and the lateral fibres from the perineal aponeurosis, the 

 anterior fibres arising from the pubis as in the male. The 

 fibres of the external layer are of a pinkish hue, being much 

 more highly colored than the other layers. 



The middle muscular layer is formed of circular fibres, 

 arranged, on the anterior surface of the bladder, in distinct 

 bands at right angles to the superficial fibres. They are 

 thinner and less strongly marked on the posterior and lateral 

 surfaces. 



The internal muscular layer is composed of excessively 

 pale fibres arranged in longitudinal fasciculi, the anterior 



