THE FROG. 123 



/i. Their movements ; best seen if the slide be 

 gently warmed, by contact with a lighted match 

 or other heating agent. They creep about in a 

 sluggish manner through the agency of the 

 above-named pseudopodia (amceboid movement). 



y. Their size; cf. generally with the red corpuscles. 



8. Their structure ; granular centrally, clear and 

 transparent peripherally: usually lodging one 

 or more clear round nuclei. 



c. Treat with acetic acid and magenta ; the nucleus 

 alone will be stained. It will be found to lodge 

 one or more small granular bodies {nucleoli). 



d. The microcytes. Very small bodies, for the most 

 part colourless, freely suspended in the plasma : 

 in shape variable; generally fusiform or ovoidal, 

 more rarely irregular. 



e. Coagulating blood. Allow a drop of blood to 

 coagulate upon a glass slide, taking care that it 

 does not dry up. Examine under a high power. 



a. ThQ plasma ; transformed into a colourless fluid 

 {serum) which is permeated by well-defined and 

 coagulate fibrin fila?nents. Note the course of 

 the latter ; they radiate from numerous foci and 

 anatomose irregularly. 



y8. The corpuscles ; the red ones show a marked 

 tendency to arrange themselves along the lines 

 of coagulation ; the white ones are largely to be 

 found, together with microcytes, in the foci of 

 the fibrin filaments. 



Epithelia. 



An epithelium consists of a layer of cells which 



lines or invests a free surface : the epidermis cover- 



