62 PRACTICAL HISTOLOGY. 



and exuding through the inclosing cement. The second 

 point to be attended to is that the slide where the cement 

 is to be applied is not wetted with glycerine, for this 

 would prevent the adherence of the cement. 



A word may here be said as to the course to be adopted 

 should any glycerine have accidentally got on to the 

 upper surface of the cover-glass. No attempt should be 

 made to wipe it off' at once, for the cover-glass will be 

 pressed upon and moved, and the preparation will pro- 

 bably be crushed and spoiled ; but time should be allowed 

 to the fixing cement to become thoroughly hard, and 

 then the glycerine can be removed without danger to the 

 tissue by means of a camel-hair pencil moistened with 

 distilled water. 



For the present it will be sufficient to conclude 

 the study of epithelium with the description of the 

 best modes of viewing ciliated epithelium, and of 

 studying the action of various reagents upon the 

 ciliary motion. The other more specialized forms 

 of epithelium, which are found in glandular organs 

 and elsewhere, will he seen and studied when the 

 several organs and parts of which they occur are 

 prepared. 



Preparation 7. Ciliated Epithelium in its 

 living state may he readily obtained from the mouth 

 and gullet of the recently killed Irog. A drop of 

 the aqueous humor should first be collected by 

 passing a capillary glass tube through the cornea 

 into the anterior chamber of the eye; the drop is 

 placed upon a slide, and then, the frog's mouth 

 being held open by an assistant, the roof is gently 

 scraped with the point of a clean scalpel, so as to 

 remove the adherent mucus. A little of the epithe- 

 lium will be brought away with this, and on placing 

 it in the fluid, and covering the preparation (taking 

 the precaution of previously placing a hair in the 

 drop), the cells may besought for with a high power. 

 For the most part they will be collected into little 

 groups of three or more, the cilia being in active 

 movement and producing currents in the liquid, so 



