76 



ENUMERATION OF BLOOD CORPUSCLES. 



[BOOK i. 



the diagram those to the left indicate lengths in micro-millimetres, those 

 to the right capacities in fractions of the cubic millimetre. 



Thus the numbers in the first row indicate that 500 /A of the tube contain 



r-^- of a cubic mm., again the numbers in the second row indicate that 

 iou 



450 /x contain ^-^ of a cubic mm. 

 lob 



The number of corpuscles in a known length of the tube has now 

 to be counted. In order to do so the slide B is placed upon the stage 

 of a microscope whose eye-piece is provided with a micrometer ruled in 

 squares. As a preliminary, however, observations must be made to find 

 the value of the squares of the eye-piece micrometer in terms of a stage 

 micrometer divided into millimetres. By drawing out or in the draw- 

 tube of the microscope the side of the large square is made to correspond 

 exactly with that of the number of micro-millimetres of the stage micro- 

 meter, placed on the slide. 



For instance one side of the large square (which is divided into 

 100 smaller squares) is made to correspond to 500 or say 450 /u,. The slide 

 with the capillary tube is now substituted for the stage micrometer and 

 the number of corpuscles contained in a certain number of the smaller 

 squares is counted. 



FIG. 13. THE CAPILLARY TUBE OF MALASSEZ' APPARATUS. Viewed in a microscope 

 provided with an eye-piece micrometer ruled in squares. Magnifying power 100 

 diameters. (Copied from Banvier.) 



Knowing first the length of the tube covered by the squares, second 

 the capacity of this length of the tube, we can by an easy calculation 

 ascertain the number of corpuscles in a cubic millimetre of the diluted, and 

 therefore also of the undiluted, blood. According to Malassez his method 



