CILIATED EPITHELIUM. 67 



of the mixture of air and chloroform vapor from the 

 bottle into the moist chamber. The cilia become 

 gradually slower and eventually stop. Now slip 

 the India-rubber tube off the bottle, and gently 

 blow air through the chamber, to displace the 

 chloroform vapor. The cilia will slowly revive on 

 the readmission of air, and will soon be found to 

 work as vigorously as ever. Like that with the 

 carbonic acid this experiment can be repeated a 

 number of times with a like result, if the chloroform 

 vapor is not allowed to remain too long in contact 

 with the preparation. 



-Preparation 13. To study the characters of the 

 individual cells a portion of membrane which is 

 covered by ciliated epithelium is macerated in some 

 fluid which softens and dissolves the intercellular 

 substance, whilst preserving the cells themselves. 

 The best for this purpose is a weak solution of bi- 

 chromate of potash (1 in 800). A large quantity of 

 this must be employed, and the tissue a piece of 

 the trachea of a rabbit or other animal, for instance 

 is left in it for about forty-eight hours. With the 

 point of a scalpel a little of the epithelium is then 

 gently scraped from the inner surface, and being 

 placed in a drop of distilled water on a slide, is 

 broken up with needles as finely as possible. A 

 small piece of hair is placed in the drop, to prevent 

 the soft, delicate cells from being crushed by the 

 weight of the cover-glass. This is now superadded, 

 and the preparation carefully examined with a high 

 power. 



Numerous completely isolated cells are seen float- 

 ing in the liquid, and these preserve for the most 

 part their natural form and retain their cilia, al- 

 though the latter are, of course, no longer in motion. 

 The bright border through which the cilia appear 

 to pass, the faintly granular cell-substance, the clear 

 nucleus with bright nucleolus in the middle, and the 

 tapering, branched extremity of the cell are, in most, 

 clearly visible. Besides these single cell*, others are 



