50 PROCESSOR A. BIRMINC4HAM, 



appendices epiploicae are found. On the transverse colon in 

 the natural position, the anterior taenia of the ascending and 

 descending colons becomes the posterior (or postero-inferior ; 

 ta3nia libra), the postero-external becomes the anterior (or 

 omental), and the postero-internal the superior or mesocolic. 

 The anterior and postero-external taenia of the iliac colon 

 pass below on to the front of the pelvic colon and rectum. 



Cmcum. — The ileo-Ccecal orifice is generally placed on the 

 posterior part of the inner aspect of the csecum ; about 

 1 to 1| inches lower down is seen the opening of the vermiform 

 appendix. 



When hardened in situ with formalin, the valve and orifice 

 present an appearance entirely different from that seen in dried 

 and distended specimens, and suggest much more closely an 

 appearance of telescoping of the small into the large bowel. 

 The two segments of the valve are also much thicker and 

 shorter, but they can always be made out, when they are found 

 to bear the same relation to one another as in the dried condition, 

 although this may be obscured by folding or ruga3. The aperture 

 may be slit-like or rounded, with sloping or infundibuliform 

 edges ; the frenula are not so prominent at times, but the whole 

 valve projects much more abruptly into the cavity of the ctecum 

 than in the distended and dried specimen. 



The upper segment in dried specimens usually projects into 

 the cavity of the caecum more than the lower, so that the 

 aperture appears to be placed between the edge of the 

 lower segment and the under surface of the upper. 



There is a little doubt, as pointed out by Symington, that the 

 efficiency of the ileo-caecal valve is largely due to the oblique 

 manner in which the ileum enters or 'invaginates ' the caecum ; 

 this oblique passage alone, as in the case of the ureter piercing 

 the wall of the bladder, would probably be sufficient to prevent 

 a return of the crecal contents. In the great majority of cases, 

 when in position within the body, the ileum is perfectly pro- 

 tected from such a return ; although, when the parts are 

 removed and distended with fluid, this often passes through 

 the valve and reaches the small intestine. Still, the value of 

 such a test, applied wlien the parts are deprived of their 

 natural support, cannot be relied upon. 



