BLOOD 



XLII. — General Properties of Blood. 



Apparatus. — Glass slides and cover glasses, magnifier, microscope, 

 needle, normal salt solution (0.6% solution), neutral carminate of 

 ammonia. 



Directions. — ^Wind a handkerchief tightly around the 

 thumb, just below the joint. Now bend the upper joint. 

 The blood will collect on the top of the thumb just below 

 the nail. Sterilize a needle by holding it a second in a flame, 

 and prick the thumb just below the nail. The blood from 

 the puncture may be easily and quickly transferred to a 

 glass sUde. 



A, With a magnifier examine a drop miounted as above. 

 Is it all Uquid? Is it the same color throughout? Describe 

 the color at the edge of the drop. Let the drop remain on 

 the slide for ten minutes and examine again. Is it Uquid 

 now? Prick at it with the needle point and describe its 

 consistency. This formation is called a clot. Examine the 

 puncture on the thumb with the magnifier. Has it stopped 

 bleeding? What is the condition of the blood on the surface 

 of the puncture? Does it resemble the condition of the drop 

 on the shde? Bind up the thumb as before and flex the 

 upper joint. Does the puncture bleed again? Wash off 

 the clot with water. Does the bleeding begin again now? 

 What is the advantage of this clotting action of the blood 

 when exposed to air? 



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