BLOOD. 35 



F. Microscopic Examination of Blood. 



I. Frog's Blood. 



1. Normal. 



Place on a slide a small drop of hlood from the heart of a frog ; 

 dilute it with a drop of normal salt solution (0"75 per cent) : put 

 on a thin cover-glass, and run a ring of oil round the edge to pre- 

 vent evaporation : examine with the high power. 



Blood consists of a colourless fluid, the liquor sanguinis 

 or plasma, in which float the Wood corpuscles. These 

 corpuscles are of two kinds. 



i. Red corpuscles. These are very numerous, pale 

 red or yellowish red in colour, and of a flattened 

 oval shape, with rounded edges and a central 

 bulging, the nucleus. The flattened shape is best 

 seen when a corpuscle turns edgeways. They 

 measure 0'0235 mm. in length by 0*0 145 mm. in 

 width ; or about yyVo ^ TsVo" ^'^ ^^ inch, 

 ii. White corpuscles. These are much fewer in number 

 and of smaller size : they are colourless, granular, 

 subspherical in shape, and exhibit " amoeboid " 

 movements. Sketch one half-a-dozen times at 

 intervals of half a minute. 



2. Action of acetic acid on blood. 



Place a fresh drop of blood on a clea7i slide : add a drop of 

 acetic acid : cover, and examine with the high power : note the 

 changes produced. 



i. Red corpuscles : the nuclei become much more 

 apparent than before, and the red colour dis- 

 appears. 



ii. White corpuscles : become clearer, and show nuclei, 

 sometimes more than one in a single corpuscle. 



II. Human Blood. 

 1. Normal. 



Prick the tip of your finger, and place a small drop of the 

 hlood on a, slide: add a drop of normal salt solution, cover, and 

 examine as before. Note the folloidng p)oints : 



i. Red corpuscles. These, which are much smaller 



