96 



SPECIAL HISTOLOGY. 



sometimes coming off together like the calyptra of a moss. 

 The addition of water to these cells produces a separation of 



Fig. 211. 



the cell contents from the broad end, giving rise, in separate 

 cells, to the appearance of a membrane thickened upon one 

 side and in series of cells or entire villi, to that of a peculiar 

 structureless coat, like the cuticle of plants; by its longer 

 action, however, or by that of the intestinal fluids, the burst- 

 ing of the cells produces apertures in them, or they become 

 distended into large pyriform clear vesicles. 



[We may here refer to the changes which the epithelial cells 

 and the villi in general undergo during digestion. The most 

 striking circumstance is the occurrence of fat in different 

 parts of the villi, which may always be observed during the 

 formation of a fatty, milk white chyle. The succession of the 

 morphological steps, at least as I have observed them in animals, 



Fig. 211. A, two villi, with their epithelium, from the Rahbit, x 73: a, epithe- 

 lium ; b, parenchyma of the villus. B, a detached sheet of epithelium, x 300 : a, 

 membrane raised up by the action of water. C, single epithelial cells, x 350 : a, 

 with, b, without, a raised-up membrane ; c, a few cells from the surface. 



