POSITION OF THE RECTUM. 57 



tines at their place of junction, and this structure is then 

 examined from without, it appears as if a transverse or half 

 circular indentation had been formed by the villous coat of the 

 great intestine, and that the internal coat of the extremity of 

 the ileum was pressed into this indentation, and united to the 

 internal coat of the great intestine which formed it ; while there 

 was a slit both in the indentation and in the end of the ileum, 

 which formed a communication between the cavity of the great 

 intestine and the ileum. The longitudinal fibres of both intes- 

 tines, as well as their external coats, seemed to be united, so as 

 to form a common cover for them ; while the circular fibres 

 were blended in the two portions of the indentation which form 

 the lips of the orifice. 



This orifice is, of course, transverse with respect to the 

 intestine. It has been observed, that there was a difference in 

 the thickness and strength of the two lips or valves ; that the 

 lower valve was the strongest and appeared to have the largest- 

 proportion of muscular fibres in its composition. At the extre- 

 mities of the orifice, and near each end of the fold or ridge, are 

 tendinous fibres, and which give strength to the structure: 

 they are called the Retinacula of Morgagni, as they were first 

 described by that anatomist. 



There is a great reason for believing that this valve cannot 

 prevent the retrograde motion of the contents of the intestines 

 in all cases ; for in some instances of hernia and of colic, matter 

 perfectly stercoraceous has been vomited, and the probable 

 inference from such a state of the ejected matter is, that this 

 matter has been in the large intestines. It is also said, that 

 suppositories arid enemata have been discharged by vomiting. 



On the right and left sides of the abdomen, the colon is in 

 close contact with the posterior surface of the cavity. The 

 peritoneum which covers this surface extends over the intestine 

 also, and thus retains it in its position. The great arch of the 

 colon, which is loose and moves far from the back of the abdo- 

 men, is invested by the two lamina of theomentum, which, after 

 surrounding it, unite again and form the mesocolon. Connected 

 with the exterior surface of the colon are many processes, com- 



