THE STOMACH AND INTESTINE. 



275 



Epithelium 

 of villus. 



The epithelial cells undergo a special metamorphosis, after 

 which, by an increased production of mucus, they change into gob- 

 let cells. From recent investigations it would seem that any 

 epithelial cell, whether it be situated upon the upper surface of a 

 villus or deep down in one of the tubules of the intestinal glands, is 

 capable of transformation into a goblet cell. The number of goblet 

 cells is subject to great variation ; they are found singly in small 

 numbers, or are very numerous, according to the stage of digestion 

 and quantity of food in the intestine. The manner in which an 

 ordinary epithelial cell changes into a goblet cell is very easily 

 explained if the mechanical action on the cell caused by an accumu- 

 lation of secretion be taken into consideration. As the secretion 

 increases in quantity the upper portion of the cell becomes distended, 

 and the remains of the 

 protoplasm, together 

 with the nucleus, are 

 pushed toward the nar- 

 row base of the cell ; 

 the cuticular zone is 

 stretched, bulges into 

 the lumen of the intes- 

 tine, and is finally perfor- 

 ated, and perhaps even 

 thrown off. In this way 

 the cell loses its mucous 

 secretion, collapses, and 

 then appears as a thin, 

 almost rod - like struc- 

 ture, with a long nu- 

 cleus. It is the gener- 

 ally accepted theory that 

 such an empty goblet 

 cell may again assume 

 the shape of an ordinary 

 epithelial cell and repeat 

 the process just de- 

 scribed. 



Leucocytes are some- 

 times found within the 

 epithelial cells, but more 

 usually between them, 

 and according to Stohr 

 (84, 89, 94), when seen 

 in these positions, are 

 in the act of migrating 



into the lumen of the intestine. That some of these cells actually 

 pass into the lumen is probably true ; but as yet no leucocytes have 

 ever been observed in the cuticula itself, and neither is the number 



- Mucosa. 



Muscularis 

 mucosac. 



Fig. 216. Section through mucous membrane 

 of human small intestine; X 88. At a is a col- 

 lapsed chyle-vessel in the axis of the villus. 



