April, 1917] Scientific Drawing in Biology 209 



SCIENTIFIC DILWVING FOR REPRODUCTION. 



Photography. 



This is very useful for whole objects, gross dissections and 

 the like, being precise and a great time saver. 



The common photograph gives no color differentiation as 

 most colors have too near the same value. If you have a print 

 from the negative made on Whatman paper you can color on 

 this. Never try to color from memory, alwa\^s have the object 

 or a similar one. One is likely to expect too much of micro- 

 photography. Diatoms, Desmids, Bacteria, Golgi prepara- 

 tions, anything with clear outlines and single colors will give 

 good results. High powers of things like cell division or tissues 

 cells are not so satisfactory for the average photographer. The 

 investigator himself sees a mental image into the photograph 

 while outsiders are bothered by details and get an unsatisfactory 

 image. A photographic plate does not distinguish between 

 opaque and transparent structures. This can be expressed in 

 water colors in a drawing. A photograph reproduces every- 

 thing with equal value; a grain of dust, an air bubble, a crack 

 or a fault in the section, all these are faithfully repeated. The 

 microscopic field is not quite flat so that details near the edge 

 will not show. One can photograph only one focus at a time, 

 whereas your drawing is the result of the study of the structure 

 at a number of levels. It gives the results of brain work on the 

 facts before you. Everything in the drawing must be in the 

 slide but everything in the slide does not have to be in the 

 drawing. The drawing should be diagrammatic but not a 

 diagram and is superior to the photograph both in clearness and 

 in truth; in clearness because unnecessary things are omitted 

 and in truth because the essentials are not obscured by 

 unessentials as in the photograph. 



Drawing. 



A scientific drawing for reproduction should be made with 

 reference to the method of reproduction. Of these there are 

 several types. 



It is obvious that those methods of reproduction will be 

 cheaper which are entirely mechanical and can be carried 

 through by the ordinary, intelligent workman. Those, on the 



