METHODS OF RESEARCH: PREPARATION OF LLUSTRATIONS 121 



portant aid to research. How important it is, will be evident 

 at once if we reflect that photography enables us to fix the thou- 

 sand and one fleeting phenomena of nature in a permanent record 

 with which to refresh our memory and from which to draw, in 

 a way quite beyond the power of former generations, convincing 

 illustrations for papers, books, and lectures Not infrequently 

 the study of a good negative reveals details overlooked on the 

 object itself. This is most important, of course, in astronomy, 

 but it also has its uses in pathology. 



Remember that one good picture is better than half a dozen 

 pages of text in hammering home your argument and that if 

 you fail to convince your readers and hearers, then your work 

 is in vain. Therefore, do not spare good illustrations. 



The following fragmentary observations are drawn from our 

 own procedure and may be of service in smoothing the way for 

 the beginner. 



Good lenses, light-proof bellows, and suitable dry plates 

 are essential to the making of good photographs. The student 

 should read what is said on this subject under Apparatus. 



Pathological subjects usually show strong contrasts and to 

 get similar contrasts on the negative often taxes the skill of 

 the expert. It took the writer and James F. Brewer two days 

 to get the result shown in Fig. 281. 



Development should be carried on in the dark as much'as 

 possible. When light is allowed to reach the developing plate 

 it should be only of a minimum brightness (very dull red) and 

 for only very brief periods, especially during early stages of 

 development, and at all stages of development in case ot plates 

 corrected for the red end of the spectrum 



For ordinary work and for certain color contrasts such as 

 white and black or red and blue. Seed's rapid No. 30 Gilt 

 Edge dry plates may be used. These are not sensitive to red 

 light, therefore contrasting reds, yellows and greens wil come 

 out dark on the prints and often be disappointingly alike, while 

 the overexposed blue and violet parts will be pale or white on 

 the prints. Consequently, for many subjects where color con- 

 trasts are desired, Cramer's Iso medium or Iso slow plates may 

 be used. Better still for this purpose are Wratten and Wain- 



