OF DRAWING MICROSCOPIC OBJECTS. 139 



In the execution of the drawing of a microscopic object it is 

 best to use good drawing paper or Bristol board, which should be 

 either pale yellow, pale green, or white, slightly tinted. It is also 

 advisable to have the paper fastened upon a smooth board. First 

 use a soft and finely sharpened black-lead pencil, in order to 

 secure the outlines and the contour of the picture. It should be 

 slightly shaded without pressure, then with bread crumbs erase 

 most of it again ; after that with a harder and finely pointed 

 pencil retrace the outlines of the first drawing, again using the 

 prism for comparison in order to make any necessary improve- 

 ments, and to secure perfect accuracy ; at this moment is the 

 proper time to do the shading, if such is required, and this can 

 easily be done with the point of a pencil and an eraser, or still 

 better with charcoal and a soft cloth. For the execution of a 

 coloured drawing in which a variety of colours are used, water 

 colours are most commonly used, and are to be preferred, but 

 coloured pencils, and even oil colours and pastel crayons may be 

 employed instead. I wish here to call especial attention to the 

 fact that in shading it is advisable to shade off the uncoloured 

 parts first with black, of course, particular care being taken that 

 the shading does not extend into the coloured field. This is 

 necessary to avoid confusion and to preserve scientific accuracy. 

 It is also decidedly recommended to use a variety of colours, 

 especially so in the drawing of very minute objects, such as 

 endothelium, and epithelium-cells, fibrous and connective tissue- 

 cells, blood and lymphoid-cells, etc. Also in the drawing of a 

 whole slide (specimen), or only a part of it, it is almost an abso- 

 lute necessity to use a variety of colours. The contrasting 

 colours will not only make a drawing or an illustration more 

 elaborate and intelligent, but decidedly more comprehensive and 

 instructive. 



Let me here refer to the pertinent and emphatic declarations 

 of Prof. Virchow, one of the most noted and expert path- 

 ologists of the nineteenth cencury, who said that he would not 

 give " ein pfennig " for illustrations, drawings, or sketches that 

 were not correct or exact, because they would invariably convey a 

 false impression. He further declares that all lectures, demon- 

 strations, original articles, or manuscripts of any kind, must be 



