STRUCTURE OF THE RECTUM. 59 



— The circular muscular fibres at the end of the rectum, are 

 so thickened as to form a sort of annular muscle, which projects 

 into the cavity of the intestine, like the pyloric valve of the 

 stomach. It is attached to the proper sphincter muscle below, 

 by cellular tissue, and like it and the muscles of the pharynx at 

 the other extremity of the canal, is in a great measure under the 

 control of the will, being supplied in part with nerves from the 

 cerebro-spinal system. It aids the sphincter in retaining the 

 faeces in the pouch of the rectum. 



— The three longitudinal muscular bands of the colon at the 

 lower edge of the sigmoid flexure, separate into fasciculi, which 

 are distributed as they descend round the circumference of the 

 intestine, and form a thick uninterrupted layer round the 

 rectum. The longitudinal fibres of the rectum have been 

 shown by Professor Horner, to terminate in delicate tendons, 

 which pass between these two sphincter muscles, internal and 

 external, and turn upwards and inwards to be inserted on the 

 inner face of the mucous membrane of the rectum. Opposite 

 the lower edge of the internal sphincter, the mucous membrane 

 is thrown into a number of plaits or folds, in which the same 

 anatomical observer has pointed out a number of irregular 

 valvular pouches which open upwards. These when diseased 

 become a source of intolerable itching and irritation, which 

 attracted the attention of Dr. Physick, who was in the habit of 

 relieving the suffering they produced by their excision.* 



The internal coat is very vascular, but the villous structure 

 is not apparent. Mucous follicles are also very numerous ; and 

 there are likewise some distinct glandular bodies exterior to this 

 coat, which vary in size in different subjects. 



— The mucous membrane of all the large intestines, when 

 examined with the microscope under water, presents scarcely any 

 appearance of villi, but exhibits every where slight honey-comb- 

 like depressions, somewhat analogous to those of the stomach. 

 It is strewed with a multitude of follicles, (distributed tanqnam 

 Stella Jirmamente, according to Peyer,) depressed and perforated in 



* For an excellent account of these parts, see article Anus, by Dr. R. Coates, 

 in the American Cyclopedia of Med. and Surg. Philadelphia. — p. 



