EPITHELIUM. 



39 



FIG. 23. 



Cilia 



Cuticle 

 Basal granules 



Protoplasmic 

 fibres 



If during life it bears on the free surface moving hairs (cilia, 

 flagella), we call it ciliated or flagellated epithelium (Fig. 22). 

 There is sometimes on the free surface of the cell a more or less 

 definite refractive border showing striations at right angles to 

 the surface. These cells are called 

 cylindrical cells with a cuticular bor- 

 der. Finally, if the upper part of 

 the cell is changed into mucus, so 

 that this region of the cell is dilated 

 in the form of a goblet, we have to 

 do with the so-called goblet cells 

 (Fig. 22). 



In ciliated cells certain details can 

 be made out which are not always 

 visible and whose study is attended 

 with great difficulties. The cilia must 

 be recognized as hair-like processes 

 of the cell protoplasm which possess 

 the power of moving uniformly and 

 in one direction. Often such cilia 

 are seen to be made up of several 

 parts which are singly or doubly, 

 strongly or weakly refractive. 



This complicated structure can be 

 made out in the schematic representa- 

 tion of the ciliated cell of Anodonta 

 shown in Fig. 23. Here the cells are 

 covered by a cuticle. Directly under 

 this there is a row of so-called basal 

 granules, which, according to the latest 

 investigations (v. Lenhossek), are to be 

 considered as centrosomes. The cilia 

 pass through the cuticula and form in 



this a series of thickenings in the form of granules (Fig. 23). 

 In the cell itself we find often in the protoplasm a series of 

 threads which begin at the basal granules, run toward the 

 nucleus, and make up the fibrillar structure of the protoplasm. 



Nucleus 



A 



sj 



Diagram of cilated epithelial cells. 

 (After Apitthy). 



