288 PKACTICAL PHOTO-MICROGRAPHY 



Camera-extension, 3 ft. 



Plate, Wratten & Wainwright's Allochrome. 



Screen, signal-green glass. 



Exposure, 3 minutes. 



Development by amidol. The preparation presents rather 

 violent colour-contrast, so this developer was used to obtain a 

 soft negative. As the contrast between the two colours with 

 which the object is stained is photographically considerable, 

 the green-glass screen gives good results owing to its general 

 absorptive power on either side of the green region in the 

 spectrum. 



PLATE III, FIG. 1. Transverse Section of Human 

 Tongue, x 50. 



Stain, haematoxylin. 



Objective, Zeiss 16-mm. apochromat. 



Projection-ocular, 2. 



Illumination, acetylene bicycle lamp. 



Condenser, back combination of Swift achromatic con- 

 denser, working at its full N.A. 



Auxiliary condenser, Nelson achromatic. 



Screen, saturated solution of picric acid. 



Camera-extension, 20 in. 



Plate, Imperial orthochromatic (extra rapid). 



Exposure, 15 seconds. 



Development, metol-hydrokinone. 



PLATE III, FIG. 2. Transverse Section of Stem of Black 

 Pepper, x 30. 



Specimen double stained with iodine-green and fuchsin. 



This specimen was an old one, and had faded very con- 

 siderably, so that the object was faintly seen, and the colours 

 were not well differentiated. 



Objective, 24-mm. achromatic, by E. Leitz, Wetzlar. 



No ocular. 



Illuminant, Nernst electric, taking 1 ampere. 



No sub-stage condenser. 



An enlarged image of the filament projected on to the 

 object by means of Zeiss Nos. I and III collecting-lenses. 



Screen, bichromate of potash and copper acetate, the 

 bichromate of potash being in excess, so that the screen was 

 of a deep yellowish-green colour. 



