32 



PHOTO-MICROGRAPHY 



Before quitting the subject, occasionally the photo-micrographer may be asked to 

 produce very low-power photographs of Pathological Microscopical Specimens 

 which are violently stained in contrast colours of which red is often a large component. 

 If these be photographed by the ordinary methods it will be found the resulting 

 prints are full of the most severe contrasts, the red- stained portions coming out 

 violently black if the rest of the print be fully developed, whereas if under-developed 

 to render this less pronounced and to show details which really do exist in the 

 negative in the red portions, the rest of the structure appears faint and ill-defined. 

 No amount of " shading in " (described later on) of the negative will cure the trouble. 

 To render a more uniform photograph resort must be had to the power which exists 

 in the hands of the photographer to lessen contrast : viz., he must use a glass of the 

 same colour as the predominant colour of the specimen. If, for example, it is one of 

 those specimens where red-stained blood-vessels or other tissue abound and are so 

 troublesome, he must reduce the severe contrast by employing a red glass of light 

 density or otherwise, which will increase the exposure for the parts not red, whereas 

 it has but little effect on those so stained. In other words a more balanced negative 

 will result. To take such a photograph he must, it need scarcely be pointed out, use 

 a red-stained plate such as a Cadet Spectrum, Lumiere's Panchromatic, or red and 

 yellow plate. He must develop too in the dark, only glancing at the picture by fits 

 and starts for a second at a time, with a very subdued green light if possible. Having 

 then produced a flatter negative, but one full of detail without such violent contrast, 

 he had better print it either by tlie platinotype process or in bromide which will be 

 spoken about hereafter. 



SECTION II.— (i) DEVELOPING THE NEGATIVE 



Before developing the negative it is necessary for the photographer to have a dark 

 room of some sort. We do not propose to dwell at length upon this matter, as it 

 seems unnecessary in a work of this nature. A dark room should have water laid on 

 with a sink and waste-pipe, a means of ventilation and also three shutters, two of red 

 fabric and one of yellow, effectually shutting off the light of a fish-tail burner which 

 should always be placed outside the apartment. All bottles should be distinctly 

 labelled in large letters so as to be easily read in the subdued coloured light. 

 Developing dishes too should be near the sink and so quickly at hand ; covers to 

 them also, made of light wood, should be provided especially ivhen working with iso- 

 chromatic plates. 



Each photographer has his own pet formulae for development, but the following. 



