LARGE INTESTINE. 737 



The Caecum (csecus, blind) (Fig. 405) is the large blind pouch, or cul-de-sac, in 

 which the large intestine commences. It is the most dilated part of the tube, 

 measuring about two and a half inches, both in its vertical and transverse diame- 

 ters. It is situated in the right iliac fossa, immediately behind the anterior 

 abdominal wall, being retained in its place by the peritoneum, which passes 

 over its anterior surface and sides; its posterior surface being connected by 

 loose areolar tissue with the iliac fascia. Occasionally, it is almost completely 

 surrounded by peritoneum, which forms a distinct fold, the meso-caecum, con- 

 necting its back part with the iliac fossa. When this fold exists the caecum 

 obtains considerable freedom of movement. Attached to its lower and back 

 part is the appendix vermiformis, a long, narrow, worm-shaped tube, the rudi- 

 ment of the lengthened cascum found in all the mammalia, except the orang- 

 outang and wombat. The appendix varies from three to six inches in length, 

 its average diameter being about equal to that of a goose-quill. It is usually 

 directed upwards and inwards behind the ca3cum, coiled upon itself, and termi- 

 nates in a blunt point, being retained in its position by a fold of peritoneum, 

 which sometimes forms a mesentery for it. Its canal is small, and communi- 

 cates with the caecum by an orifice, which is sometimes guarded with an incom 

 plete valve. Its coats are thick, and its mucous lining furnished with a large 

 number of solitary glands. 



Fig. 405. The Caecum and Colon laid open to show Ileo-caecal Valve. 



Ileo-csecal Valve. The lower end of the ileum terminates at the inner and 

 back part of the large intestine, opposite the junction of the caecum with the 

 colon. At this point the mucous membrane forms two valvular folds, which 

 project into the large intestine, and are separated from each other by a narrow 

 elongated aperture. This is the ileo-ca3cal valve (valvula Bauhini). Each fold 

 is semilunar in form. The upper one, nearly horizontal in direction, is attached 

 by its convex border to the point of junction of the ileum with the colon; the 

 lower segment, to the point of junction of the ileum with the caecum. Their 

 free concave margins project into the intestine, separated from one another by 

 a narrow slit- like aperture, directed transversely. At each end of this aperture 

 the two segments of the valve coalesce, and are continued, as a narrow mem- 

 branous ridge, around the canal of the intestine for a short distance, forming 

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