PELVIS MINOR 465 



plexus, associated with the bladder, the seminal vesicles, and 

 the vas deferens; and \^\Q pro static plexus, connected with the 

 prostate. The prostatic plexus proceeds forwards between the 

 prostate and the levator ani, and sends branches, called the 

 cavernous nerves, to the penis. 



Trunci Sympathici. The sympathetic trunks reach the 

 pelvis considerably reduced in size. They pass downwards 

 along the medial margins of the anterior sacral foramina, 

 and they end in the median plane, in front of the coccyx, 

 in a minute unpaired ganglion, called the ganglion impar. 

 There are generally four ganglia on the pelvic portion of 

 each sympathetic trunk, and each ganglion is connected with 

 one of the sacral nerves by a grey communicating ramus. 

 Some of the branches from the ganglia are distributed 

 to the anterior surface of the sacrum, around the middle 

 sacral artery. From the upper ganglia branches proceed 

 to the pelvic plexuses, and from the ganglion impar branches 

 are given to the parts about the coccyx and to the glomus 

 coccygeum. 



Glomus Coccygeum (O.T. Coccygeal Body). This is a 

 lobulated body, about the size of a small pea, which lies in 

 front of the tip of the coccyx. It is composed of masses of 

 polyhedral cells, intermingled with strands of connective 

 tissue, numerous sympathetic nerve twigs, and branches of 

 the middle sacral artery. Its function is unknown. 



Dissection. The vessels and nerves passing to the viscera 

 should be divided and the viscera should be removed, and the 

 structure of the walls of the rectum and bladder should be 

 examined. 



Structure of the Rectum. The rectum possesses the 

 following coats: i. Serous. 2. Fascial. 3. Muscular. 4. 

 Submucous. 5. Mucous. 



The peritoneal coat, and the fascial coat, derived from 

 the visceral layer of the pelvic fascia, have already been 

 examined. 



The Muscular Coats of the Rectum. The muscular coats 

 of the rectum are strong. They consist of an external longi- 

 tudinal and an internal circular layer of involuntary or un- 

 striped muscle-fibres. The longitudinal fibres are continuous, 

 above, with the three longitudinal bands of the colon. As 

 the three bands pass downwards the fibres which compose 

 them spread out to form a continuous layer round the rectum. 



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