no NATURALISTS' ASSISTANT. 



For scientific work "bristol board" and a "six H" lead 

 pencil produce the best results. The shades may be put in with 

 India ink and a camel's hair or, better, a sable brush. In 

 case it be desired to color a drawing, water colors are best, 

 and the moist water colors are the most convenient to use. 



It is frequently desirable to use certain colors for certain 

 organs and thus through a series of drawings to indicate the 

 parts with similar functions and the following list embraces 

 the conventional colors most used. 



White or neutral tint, nerves. 

 Red, heart and arteries. 

 Blue, veins. 



Brown, the alimentary canal. 

 Green, liver. 

 Purple, renal organs. 

 Yellow, female sexual organs. 

 Orange, male sexual organs. 



In a series of drawings with these conventional tints the 

 eye readily appreciates the principal features of the anatomy 

 without the aid of descriptive text. Other organs than those 

 enumerated may be left blank or colored according to the 

 fancy of the artist. 



The various photographic processes of reproducing illus- 

 trations have lately acquired great prominence and a few 

 hints on preparing drawings for the photographer may prove 

 of use. 



The "direct transfer " process of the Heliotype Company 

 is but poorly fitted for scientific work and the results are very 



