CILIATED EPITHELIA. 



3 1 



FIG. 32. CELLS OF THE EFFERENT 

 DUCTS OF THE TESTIS OP A 

 MOUSE. (After Fuchs.) 



To show terminal bars; cuticular 

 border (in b) ; diplosomes, and 

 cilia (in c). 



of cilia is effective in one direction only, so that mucous or solid particles 

 may be swept by their action across the surface of the epithelium, for 

 example from the trachea to the mouth. In the lower animals the stroke 

 may be reversed under certain conditions. Or- 

 dinarily the student can merely detect the pres- 

 ence or absence of cilia in a given specimen. 

 Under favorable conditions investigators have 

 observed that each cilium is connected with a 

 granule or pair of granules, the basal body, 

 near the upper surface of the cell, "and several 

 agree that these arise by division of the cen- 

 trosome. In Fig. 32, a, the cell contains a 

 single diplosome (centrosome) in characteristic 

 position; b has four diplosomes; and c is cili- 

 ated with basal bodies similar to diplosomes. 

 Apparently no ciliated cell has been observed 

 in mitosis. Fig. 33, a, is a diagram to show that cilia may extend through 

 the top plate into the protoplasm, and obscure modifications of the upper 

 part of the protoplasm may sometimes be seen with ordinary magnifica- 

 tion. The row of diplosomes may appear to form a single or double 

 transverse line. 



The cells known as spermatozoa are each provided with a single, 

 very long, motile process, such as is called a 

 flagellum. It develops in relation to the cen- 

 trosome, as will be described in connection with 

 the testis. Some so-called cilia are non-motile 

 prolongations of the filar mass of the proto- 

 plasm, and seem to be concerned with the dis- 

 charge of secretion. They have no basal bodies 

 and lack the distinctness of true cilia, generally 

 appearing in conical clumps like the hairs of 

 a wet paint brush. Such cilia are found in 

 the epididymis (Fig. 33, b). In certain of the 

 kidney cells there are short, thick, non-motile 

 processes, described sometimes as rudimentary 

 cilia, sometimes as a cuticula, and known as 

 the " brush border." The cells which line the 

 central canal of the nervous system develop 

 processes which are not true cilia. Finally, in what is called neuro-epi- 

 thelium, as in the taste buds, the epithelial cells have one or more slender 

 processes apparently designed to receive stimuli, and the function of the 



FIG. 33. 



a, Diagram of a ciliated cell (after 

 Prenant), showing vibratile 

 cilia ; b, cells of the human epi- 

 didymis (after Fuchs), show- 

 ing non-motile cilia. 



