DRAWINGS 519 



made to acquire some skill in this direction. The problem of the micros- 

 copist, who has but little to do with the third dimension, is relatively 

 simple. A few suggestions may be given. 



Generally sections are stained in different colors, and the question 

 at once arises how to represent these with the pencil. The accompanying 



FIG. 494. DIAGRAMS SHOWING THE WAY IN WHICH THE SHADE VALUES OF THE PRIMARY 

 SECONDARY AND TERTIARY COLORS MAY BE REPRESENTED IN TERMS OF BLACK AND WHITE 

 (Lee, in Hardesty's "Laboratory Guide;" Blakiston, 1908.) 



figures indicate the way in which this is done, the primary colors being 

 shown in the inner ring, and their combinations in the outer rings. Red 

 being a brighter color than blue is to be made lighter. Orange, a com- 

 bination of the two brightest of the primary colors, should be lighter than 



