BLOOD CELLS 23 



Example 6. — Blood Cells 



Material. — Chloroform a frog by placing it in a small 

 box or under a bowl, with a piece of cloth or a small 

 wad of cotton, upon either of which a few drops of 

 chloroform have been poured. In four or five minutes 

 the animal will be dead, though its muscles may twitch 

 if stimulated. Such movements are purely reflex. Ex- 

 pose the heart by making an incision with a scalpel or 

 with fine scissors along the median line through the 

 skin and muscles of the abdomen, and turning back the 

 flaps of skin and muscle. The heart will then be seen 

 beating in the pericardium. Cut into this, and lay bare 

 the tip of the heart. Have at hand, also, a hand-lens, 

 compound microscope, one per cent, acetic acid, strong 

 aqueous solution of magenta, warm-stage, indigo or car- 

 mine (dry), dilute yeast, piece of ice, alcohol lamp, .75 

 per cent, salt solution, pipette, and glass rod. 



Method of Examination. — Put a drop of normal (.75 

 per cent.) salt solution in the centre of a slide, lay a 

 scrap of paper by the side of the drop, snip off the tip 

 of the frog's heart, collect a drop of blood in a pipette 

 or on the end of a glass rod, and mix the drop with the 

 salt solution. Put on the cover-glass and examine with 

 a low, afterwards with a high power. Lay the frog 

 away on a moist cloth or sponge under a bowl so as to 

 prevent the body from becoming dry. 



Note that the blood consists of a fluid or plasma in 

 which float two kinds of cell — red and colorless. 



MOEPHOLOGT 



a. The red cells or red corpuscles. — Are they abun- 



