184 ANATOMY OF THE ABDOMEN, ETC. 



intestine ; it is formed from the mucous coat of the caecum, 

 and, within that part of the intestine, appears as a trans- 

 verse, elliptical opening, formed by two lips, which, when 

 closed, overlap each other, and which any distension of the 

 caecum can only close more effectually. 



The walls of the intestines are composed of four coats, 

 viz : peritoneal, muscular, cellular, and mucous. The peri- 

 toneal coat completely surrounds the small intestine, its 

 two layers meeting to form the mesentery. With the 

 exception of the caecum, which it wholly invests, and 

 furnishes with a mesentery, it only partially covers the 

 large intestine; passing over its anterior portion, and then 

 being reflected on to the parietes of the abdomen, it leaves 

 the posterior wall in direct contact with the iliac fascia. 

 Attached to the peritoneal surface of the large intestine, 

 small fatty bodies are sometimes seen, hanging off in a 

 fringe-like manner; they vary in number and size, and are 

 called appendices epiploicde. If the peritoneum be peeled 

 off from the intestine, the miLscular coat, consisting of 

 longitudinal and transverse fibres, will be seen beneath it ; 

 the longitudinal fibres are external to the circular, but the 

 latter are thicker and most developed, except in the large 

 intestine, where the muscular fibres are chiefly collected in 

 the longitudinal bands characteristic of that part of the 

 tube. The mucous coat is continuous throughout the whole 

 alimentary canal. In the upper part of the small intestine 

 it lies in a series of transverse folds, called valvulse conni- 

 ventes ; these gradually disappear in the ileum. In the 

 large intestine it is thrown into sharp ridges, correspond- 

 ing to the constrictions of its sacculi. The sub-mucous 

 cellular tissue connecting the mucous and muscular coats, 

 which may be demonstrated by stripping off the mucous 

 membrane, is sometimes described as a fourth coat, called 

 the cellular. 



The intestines are furnished with certain GLANDS, which 

 may be seen upon the surface of the mucous membrane. 

 The solitary glands are white, rounded, and slightly promi- 

 nent bodies, scattered over the surface of both large and 

 small intestine, in the former being found chiefly in the 

 caecum. The follicles of Lieberkuhn, found also in both 

 large and small intestine, consist of little follicles with a 

 minute orifice, hardly perceptible. The agminated, or Peyer's 

 glands, belong chiefly to the ileum, and exist only in the 

 small intestine ; they are of an oblong shape, have a granu- 



