ENUMERATION OF BLOOD-CORPUSCLES 



87 



In disease the percentages above given are subject to much 

 variation. 



Cells that contain basophile granules are occasionally seen in 

 normal human blood, as well as in disease. Their significance js 

 not understood. They are not demonstrated by the Ehrlich tri- 

 color stain. They are easily found in the blood of the Amphibia, 

 by staining with basic dyes. 



There is some reason for believing that the lymphocyte is the 

 youngest form of leucocyte, and that the other varieties are 

 developed from it in succession while circulating in the blood- 

 channels. 



ENUMERATION OF BLOOD - CORPUSCLES 



The number of blood -corpuscles in a cubic millimeter of blood 

 may be determined quite accurately by means of the haemocyto- 

 meter. To lessen the labor of counting, the blood is diluted with 

 normal salt solution or Toison's fluid.* 



The blood is drawn into the pipette, Fig. 61 A, to the point marked 0.5, or to 

 1.0, and then the fluid is drawn in till the bulb is filled to 101.0. With the 

 finger on the end of the pipette it is shaken to mix the blood with the solution. 

 Discarding the first drop, a small quantity is placed in the center of the small 



FIG. 62. PLATE AND RULED DISK OF THE H^MOCYTOMETEK. 



disk in the middle of the slide, Fig. 62. The cover-glass, which goes with the 

 instrument, is placed. over the drop. Air bubbles are to be avoided, and no dust 



*Toison's fluid 



Methyl violet. 5B 025 grams. 



Sodium chloride 1. 



Sodium sulphate 8. 



Glycerin 30 c.c. 



Water 160 c.c. 



The leucocytes are stained faintly purple. The red blood-cor-puscles retain their normal color 

 and form. 



