PELVIS 609 



the rectum, and the prostatic 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. 



Gangliated Cords of the Sympathetic. The sympathetic 

 cords reach the pelvis considerably reduced in size. They pass 

 downwards along the medial margins of the anterior sacral 

 foramina, and they end in the medial plane, in front of 

 the coccyx, in a minute unpaired ganglion, the ganglion 

 impar. There are generally four ganglia on the pelvic 

 portion of each sympathetic cord, and each ganglion is con- 

 nected with one of the sacral nerves by a grey communicating 

 root. The other branches from the ganglia are distributed 

 chiefly 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 

 coccygeal body. 



The 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 inter- 

 mingled with strands of connective tissue, numerous sym- 

 pathetic nerve twigs, and branches of the middle sacral artery. 

 Its function is unknown. 



Dissection. The viscera should now be removed, and the structure of 

 the walls of the bladder and rectum 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 serous coat, and the fascial coat derived 

 from the visceral layer of the pelvic fascia, have already 

 been examined. 



Muscular Coat of the Rectum. This coat is strong, and is 

 composed of an external longitudinal and an internal circular 

 layer of involuntary or unstriped muscle-fibres. The longi- 

 tudinal fibres are continuous above with the three longitudinal 

 bands of the colon. As these bands pass downwards the 

 fibres which compose them spread out to form a continuous 

 layer round the rectum. The layer is not, however, uniformly 

 thick on all aspects of the gut, for in front and on the back 

 the fibres are massed to form two broad bands, which main- 



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