52 THE STRUCTURE OF THE FOWL 



numerous columnar cells possess a thick 

 striated border at their free ends. The goblet- 

 cells produce a glairy, transparent material 

 known as mucin, and are much more 

 numerous in the large intestine than they 

 are in the small gut. Goblet-cells are least 

 numerous towards the summit of a villus. 



In the interior of a villus, and composing 

 the greater part of its bulk, is a cellular stroma 

 containing small blood-vessels and an absorbent 

 vessel. In addition, the villus contains a 

 certain amount of muscular tissue, the cells 

 of which are arranged parallel to its long axis. 



In the duodenum, and in some regions of 

 the caeca, the villi are replaced by definite folds 

 of mucous membrane. In the duodenum in 

 particular these folds are distinct, irregular in 

 disposition, and frequently united to each other. 



Between the villi are the openings of the 

 simple, tubular intestinal glands, each lined by 

 a single layer of gi'anular epithelial cells, 

 among which, especially in the large intestine, 

 are goblet cells. 



Throughout the whole of the intestine 

 lymph nodules are present in the mucous 

 membrane. In some places, notably in the 

 caeca (Fig. 26), these are so numerous as to 



