ACTION OF THE LAEGE INTESTINE. 385 



tirely free, and is sometimes provided with a short fold of 

 mesentery for a part of its length. The coats of the appen- 

 dix are very thick. The muscular coat consists of longitudi- 

 nal fibres only. The mucous membrane is provided with 

 tubules and closed follicles, the latter frequently being very 

 numerous. This little tube, which is only about one-third 

 of an inch in diameter, generally contains a quantity of clear, 

 viscid mucus. Particles of faecal matter and extraneous sub- 

 stances, such as seeds, sometimes find their way into its cavi- 

 ty, and producing ulceration, they may escape into the peri- 

 toneal cavity and induce fatal inflammation. 1 The uses of 

 the vermiform appendix are unknown. 



Ileo-ccecal Valve. The most interesting anatomical pecu- 

 liarity of the caecum is the opening by which it receives 

 the contents of the small intestine. This opening is ar- 

 ranged in the form of a valve, known as the ileo-csecal valve, 

 situated at the inner and posterior portion of the caecum. 

 The small intestine, at its termination, presents a shallow 

 concavity, which is provided with a horizontal button-hole 

 slit opening into the caecum. The surface of the valve 

 which looks toward the small intestine is covered with a mu- 

 cous membrane provided with villi and in all respects re- 

 sembling the general mucous lining of the small intestine. 

 Viewed from the caecum, a convexity is observed correspond- 

 ing to the concavity upon the other side. The caecal surface 

 of the valve is covered with a mucous membrane identical 

 with the general mucous lining of the large intestine. It is 

 evident from an examination of these parts that pressure 

 from the ileum will open the slit and allow the easy passage 

 of the semi-fluid contents of the intestine ; but pressure from 



1 During intra-uterine life, the caecum is relatively much larger than in the 

 adult. It afterward retracts in its lower half or two-thirds to about the diam- 

 eter of a crow-quill, and this forms the appendix vermiformis. This appendix 

 exists only in man and the quadrumana. (SAPPEY, Traite d 1 Anatomic Descriptive, 

 Paris, 1857, tome iii., p. 202.) 

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