CAECUM AND VEKMIFOKM PKOCESS. 



1215 



always be distinguished, and are found to bear the same relation to one another as in the dried 

 condition, although this may be obscured by foldings or rugae. The aperture may be slit-like or 

 rounded, with sloping or funnel-shaped edges ; the frenula are not so prominent at times ; but 

 the whole valve projects mucn more abruptly into the cavity of the caecum than in the distended 

 and dried specimen. 



Structure of the Valvula Coli. Each labium of the valve is formed of an 

 infolding of all the coats of the gut, except the peritoneum and the longitudinal muscular 

 fibres, and consequently consists of two layers of mucous membrane, with the sub- 

 mucosa and the circular muscular fibres between, all of 

 which are continuous with those of the ileum on the one 

 hand and of the large intestine on the other. The surface 

 of each labium turned towards the small intestine is 

 covered with villi, and conforms in the structure of its 

 mucous membrane to that of the ileum ; whilst the 

 mucous membrane of the opposite surface resembles the 

 mucous coat of the large bowel. 



UCOUS MEMBRA 



THROUGH THE JUNCTION OF THE 

 ILEUM WITH THE CAECUM, TO SHOW 

 THE FORMATION OP THE VAL- 

 VULA COLI. 



In the dried specimen the superior labium usually projects 

 further into the cavity of the caecum than the inferior, so 

 that the aperture appears to be placed between the edge of 

 the inferior segment and the inferior surface of the superior. 



There is little doubt that the efliciency of the valvula 

 coli is largely due to the oblique manner in which the ileum 

 enters or in vagina tes the large intestine ; 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 C33cal contents. In the great majority of cases, when in 

 position within the body, the ileum is perfectly protected from ----- 

 such a return, although when the parts are removed, and then FlG> 953. DIAGRAMMATIC SECTION 

 distended with fluid, this fluid often passes through the valve, 

 and reaches the small intestine. Still, the efficiency of such a 

 test, applied when the parts are deprived of their natural 

 supports, cannot be relied upon. 



The size of the segments of the valve, as seen in the dried 



condition, varies considerably ; they are sometimes very imperfect ; and even the absence of 

 both has been recorded. But here again there is danger of falling into error, through examining 

 the parts under such artificial conditions. 



Types of Csecum. Three chief types of caecum may be distinguished the fatal type, conical 

 in shape and nearly symmetrical, with the inferior end gradually passing into the vermiform 

 process ; the infantile, in which the passage from the caecum to the vermiform process becomes 

 more abrupt, the lateral wall more prominent, and the whole sac more asymmetrical ; and the lop- 

 sided adult form, as described above, which is the condition found in 93 or 94 per cent, of adults. 



Structure. Nothing in the arrangement of the mucous and submucous coats calls 

 for special notice. The taenise or longitudinal bands of the muscular coat all spring 

 from the base of the vermiform process (Fig. 954) ; the anterior runs up on the front, 

 medial to the main prominence of the caecum ; the postero-lateral runs up behind this 

 prominence ; whilst the postero-medial passes directly upwards behind the ileum (Fig. 

 954). The longitudinal fibres on the superior aspect of the ileum partly join the postero- 

 medial tsenia ; those on the anterior and posterior aspects join the circular fibres of the 

 large gut. 



The serous coat has, in connexion with it, certain folds and fossae which are described 

 1218. 



Processus Vermiformis (Fig. 954). The vermiform process (O.T. appendix, 

 vermiform appendix) is a worm-like tubular segment which springs from the 

 medial and posterior part of. the caecum about 1 to 1 \ inches (2*5 to 3'75 cm.) below 

 the ileo-caecal orifice. From that point it generally runs in one of three chief direc- 

 tions, namely (1) over the brim, into the pelvis ; (2) upwards behind the caecum ; 

 or (3) upwards and medially, thus pointing towards the spleen ; each of which has 

 been considered to be the normal position by one or more observers. In the first 

 of these situations it is quite evident as it hangs over the pelvic brim ; in order 

 to expose it in the second, the caecum must be turned upwards ; whilst, in the third 

 position, it lies behind the end of the ileum and its mesentery, and these must 

 be raised up in order to display it. In addition to the positions just mentioned, it 



