VISIBLE AND U.V. ABSORPTION HISTOSPECTROSCOPY 



117 



prisms of the monochromator are 5 cm. long and 4 cm. high; the 

 table on which they are mounted can be rotated by means of a 

 slow-motion screw. The collimating lens has a focal length of about 

 8 cm. and the telescope lens about 80 cm.; both are held in adjustable 

 brass mountings and these with the prism table are fastened to an 

 iron plate on leveling screws. The whole apparatus is enclosed in a 

 wooden box with the required apertures. A spectrum from the first 



Photoelectric cell 



Amplifier Lii 

 Galvanometer ( o 



Ultraviolet 

 light source 



^ 



Quariz 

 monochromator 



CENTRAL 



BEAM 



k 



tf 37 



Quartz obiective 



Quartz slide 

 and cover slip 



Quartz condenser 



^>^ — - — y^ 



^Quartz ^ 



reflector 



Fig. 10. General arrangement of light source, 

 monochromator, microscope, and measuring device 

 for determining the absorption of ultraviolet Hght 

 by minute volumes of tissue. From Gersh and Baker 

 (1943) 



prism, without entering the second, passes out of one of these 

 apertures to fall on a calibrated wall scale 2 meters distant. By this 

 means the prisms can yield any chosen wavelength when manually 

 adjusted. 



A Zeiss quartz microscope of Kohler design is mounted on a 

 leveling table so that it can receive the radiation reflected by a 

 quartz right-angle prism. In order to fill the objective field, the 

 substage condenser is focused on the field of the telescope lens rather 



