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CHAPTER VII 



HIGH-POWER, OR CRITICAL PHOTO-MICROGRAPHY 



Section (i) In this division it is shown how to photograph several types of 

 different test objects, to which is added a few remarks on the special development of 

 the negatives required, whilst in 



Section (ii) The photography of bacteria is fully explained. 



High-power photo-micrography is the ambition of the photographer. To approach 

 perfection in it requires more than a trial or two on behalf of the operator, whilst 

 to bring it to absolute perfection he must become a microscopist of the highest 

 order. Dr. Dallinger has said that "exhibiting specimens really well, is 'an art,' 

 and not one to be Hcquired in a moment." 



In both sections of this chapter the theory involved is not now considered, nor 

 the reason " why " gone into : they consist, in reality, of a series of short paragraphs 

 showing what, in the writer's experience, is necessary with respect to the general 

 arrangement of the apparatus to produce photographs of certain well-known test 

 objects, special types of differing difficulty being selected. They are all illustrated, 

 and reference to the plates will be made from time to time. 



Polyxenus lagurus. — The hair of the pencil tail. Fig. 7, Plate III. 



We commence with one of the easiest tjpes of specimen, it is the hair of the 

 Pencil tail, and for that we use a sixth apochromatic, though we do not here imply 

 that good photographs cannot be taken with monochromatic light, stained plates and 

 achromatic objectives ; but we feel confident, for the best results, nothing but the 

 purest of apochromatics by either Powell & Lealand, or Zeiss, and perhaps Reichert 

 or Leitz, should be used. 



This innocent-looking little hair is an excellent test for colour correction of the 

 objective, and few lenses but the very best will show the object white between its 

 border lines. If a photograph be taken, then, with a badly corrected objective, the 

 white portions will look dirty, and the object, instead of standing out cleanly cut. 



