BY DR. KLEIN. 37 



needles (avoiding every kind of mechanical injury) in such a 

 manner that the peritoneal surface looks upwards : a drop of 

 half per cent, solution of common salt is then placed on the 

 under surface of the cover-glass, which is cautiously applied. 

 In such a preparation we find places in which a bird's-eye view 

 is obtained of the cilia in motion, as well as others, where, as 

 in the preparation from the throat of the frog, we see the same 

 in profile. The cells, which bear the cilia, are not cylindrical, 

 but form a pavement endotheliurn, the elements of which are 

 granular. We shall have occasion to return to these cells in 

 the description of the endothelium of the septum. The sto- 

 mata are almost always guarded by the cells above described. 

 If we are uncertain of the direction in which the cilia strike, or 

 if we wish to demonstrate this positively, we should transmit 

 through the preparation, by the method of irrigation described 

 in Chapter I., coloring matter, or some similar substance, in a 

 finely divided state, such as ground animalchareoal, cinnabar, or 

 Indian ink, suspended in half per cent, solution of common salt. 

 We shall then be able to recognize, from the direction in which 

 the particles are driven, the direction in which the ciljajsJLrike. 



Forms of Ciliated Epithelium. For the study of the 

 various forms of ciliated cells, we remove a mucous membrane 

 covered with these from a freshly-killed animal, and place 

 small pieces of it in a sherry-colored solution of bichromate 

 of potiish. After they have lain in the liquid for twenty-four 

 hours or more, we scrape with a scalpel from the free surface 

 a little of the epithelium place it on a slide in a small drop 

 of bichromate of potash solution or of common water, reduce 

 it to fragments with the handle of a needle and cover it. The 

 most suitable objects for such a study are the trachea of a 

 mammal, the bell-shaped extremity of the Fallopian tube of 

 the sow, and the mucous membrane of the mouth, throat, and 

 oesophagus of the frog. By this mode of preparation the cells 

 are preserved very perfectly. In the long conical cells with 

 ciliated bases we have to notice the granular protoplasm which 

 composes the body, the brjgh-t basal border, the sharply- 

 defined ovoid nucleus, with its large single or double nucle- 

 olus; tfiejong filaments, simple or divided processes which 

 penetrate between the cells of the deeper layers, and finally 

 the cilia which pass out from the central protoplasm, perfora- 

 ting He basal border. 



Besides these, we find intermediate forms of ciliated cells, 

 which are shorter and broader, and which run out into one or 

 two short, thick processes; and varying forms of spindle- 

 shaped cells, which, as we may convince ourselves, in large 

 flakes of epithelium, wedge themselves, by means of processes 

 of greater or less thickness, between the processes of the 

 ciliated elements. They possess, likewise, an ovoid nucleus. 



