EPITHELIUM 153 



and then cleared in oil of cloves. Mount in balsam, and examine 

 with the hi<jh power, 



i. The superficial layer consists of long narrow 

 columnar cells, packed together side by side, with 

 nuclei at their inner or deeper ends. 



HI. Ciliated Epithelium. In this the cells, which are usually 

 columnar, bear at their free ends tufts of exceedingly fine hair- 

 like processes cilia which, when living, exhibit active lashing 

 movements. 



a. Isolated cells. From trachea of rabbit : isolated by 



maceration for 24 hours in Ranvier's alcohol ; stained 

 with picro-carmine, and scraped into glycerine. 



Mount a small drop of the prepared specimen in glycerine ; 

 paint a ring of cement round the cover-glass ; examine with the 

 high power, and note : 



i. The shape of the cells : their nuclei ; and the tuft 

 of cilia at one end of each cell. 



b. Cells in situ: ciliary movement. 



Snip off a small piece of epithelium from the roof of the 

 mouth of a freshly killed frog, near the eyeball; mount in normal 

 salt solution, and add a small drop of gamboge water to render 

 the movements more clearly visible ; examine with the high power : 

 note : 



i. The currents due to the ciliary motion. 



ii. The movements of the individual cilia : best seen 

 when the specimen is beginning to die, and the 

 movements to slacken in speed. 



IV. Stratified Epithelium. This is characterised by the 

 epithelium being several cells in thickness. 



Take a prepared section of oesophagus of rabbit, or of conjunc- 

 tiva of rabbit or pig, which has been hardened in chromic acid, 

 stained, and cleared in oil of cloves. Mount in balsam, examine 

 with the high power, and note : 



i. The stratification of the epithelium. 



ii. The transition from the deeper spherical or columnar 

 cells to the superficial squamous cells. 



