LESSON XI 



THE BLOOD (Continued) 



THE COUNTING OF HUMAN BLOOD-CORPUSCLES. SPECIFIC GRAVITY 

 AND APPEARANCE OF BLOOD 



1. Microscopic Examination of Blood. Pith a frog and open the 

 abdomen. Incise the ventricle and allow a few drops of blood to fall 

 into 20 c.c. of a solution of 0.7 per cent, sodium chlorid. Place a drop 

 of this mixture upon a glass slide and examine the corpuscles under the 

 microscope. Note their shape, size, and nucleus. 



Place a droplet of blood from your finger upon a glass side and spread 

 it out by drawing the edge of a cover-glass through it. Note the shape 

 and size of the corpuscles. Move the cover-glass slightly so as to 

 obtain a lateral view of some of them. Note their shape. 



Insert a thin layer of porous wood under the skin of the dorsal 

 lymph-sac of a normal frog. Allow it to remain there for twenty-four 

 hours. Remove it and carefully wash it in a few drops of normal saline. 

 Place a drop of the latter upon a slide and examine it for leukocytes. 

 Study the movements of one of these, making sketches in gross outline 

 at intervals of three minutes. If not actively moving, gently warm the 

 slide over an alcohol lamp. Add a few granules of powdered India-ink 

 and observe the manner in which the leukocytes envelop this foreign 

 substance. 



2. Counting of Human Red Cells. Wash the tip of your finger 

 with a cloth moistened in alcohol. Allow it to dry. Pierce the skin 

 of its dorsal surface with a lancet-shaped needle and squeeze the tissues 

 to obtain a droplet of blood as quickly as possible. Count the number 

 of the red corpuscles in the manner described in the preceding lesson. 

 Obtain a fresh droplet of blood and determine the number of the leu- 

 kocytes. 



3. Simultaneous Count of Red and White Corpuscles. Proceed as 

 described above when counting the red cells alone. Add a stain to the 

 diluting fluid that will color the white cells only, for example: 



Methyl violet, 0.025 gram 



Sodium chlorid, 1.0 



Distilled water, 100 c.c. 



Count the red cells in a group of 36 spaces. Then count the white 

 cells in all of the 9 square millimeter spaces. Repeat with two or three 

 different samples. Obtain the average. Multiply by 4000 and again 

 by 100. 



4. Estimation of the Percentage of Hemoglobin. Procure a Fleischl 

 hemoglobinometer, glover's needle, and a small beaker. The metallic 



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