246 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
tion, making the necessary adjustment in the vertical height of the 
condenser. 
Medallion A (fig. 18) shows the figure of squares superposed upon 
the micrometric ruling of an ordinary stage micrometer, which is ruled 
in tenths of millimetres. Any line in the projection-scale can be super- 
posed upon any line of the stage micrometer by a mere movement of the 
mirror round its vertical or horizontal axis. When any one line of the 
projection-scale has been superposed upon any line of the stage micro- 
meter, all the other lines can be made to correspond by adjusting the 
distance between the projection-scale and the Microscope. 
Medallion B (fig. 19) shows the application of the projection-scale * 
to the enumeration of red and white blood-corpuscles. The appearances 
shown in the medallion are obtained by substituting for the stage micro- 
meter, shown in medallion A, a specimen of 200-fold diluted blood, 
which has then been filled into an unruled hasmc-cytometer-cell of a depth 
of 0*2 mm. 
The white bl col -orpuscles are most conveniently enumerated by 
* Projection-scales of this pattern maybe obtained from Mr. A. E. Dean, jun.^ 
73 Hatton Garden, E.C. 
