I.] THE FROG. 123 



p. 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 (amoeboid 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. 



e. 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 or blood platelets. 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. The plasma ; transformed into a colourless fluid 

 (serum) which is permeated by a coagulate 

 material, fibrin. 



/?. The corpuscles ; the red ones show a marked 

 tendency to arrange themselves in radiate series ; 

 the white ones are largely to be found, together 

 with microcytes, in the foci of the radii. 



y. Wash with water. The colouring matter of the 

 red corpuscles will be dissolved; note the 

 fibrin filaments, for the most part coincident 

 with the above-named radii. 



2. Epithelia. 



An epithelium consists of a layer of cells which 

 lines or invests a free surface : the epidermis cover- 



