.LARGE INTESTINE. 6U 



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

 surrounded by peritoneum, which forms a distinct fold, the mesocaecum, connecting 

 its back part with the iliac fossa. This fold allows the caecum considerable 

 freedom of movement. Attached to its lower and back part, is the appendix 

 vermiformis, a long, narrow, worm-shaped tube, the rudiment of the lengthened 

 ca3cum found in all the mammalia, except the ourang-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 terminates in a blunt point, being retained 



Fig. 339. The Czccnm and Colon laid open to show the 

 ileo-caeoal Valve. 



in its position by a fold of peritoneum, which sometimes forms a mesentery for it. 

 Its canal is small, and communicates with the cajcum by an orifice which is some- 

 times guarded with an incomplete valve. Its coats are thick, and its mucous lining 

 furnished with a large number of solitary glands. 



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

 back part of the large intestine, opposite the junction of the ca3cum with the 

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

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

 elongate aperture. This is the ileo-caecal 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 being connected at the point of junction of the ileum with the caecum. 

 Their concave margins are free, project into the intestine, separated from one an- 

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

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

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

 the fraeua or retinacula of the valve. The left end of this aperture is rounded ; 

 the right end is narrow and pointed. 



Each segment of the valve is formed of a reduplication of the mucous mem- 

 brane, and of the circular muscular fibres of the intestine, the longitudinal fibres 

 and peritoneum being continued uninterruptedly across from one intestine to the 



