STAINING, PRACTICAL AND THEORETICAL 



It is proposed to deal only with fluorochromy in the short space 

 of this chapter. 



Fluorescent dyes and other substances used for this purpose are 

 known collectively as " fluorochromes " ; these materials are 

 selectively absorbed by certain parts of the cell. When tissues, 

 bacteria or protozoa, which have undergone treatment with fluoro- 

 chromes are examined under the microscope, using ultraviolet 

 light instead of transmitted light of the visible spectrum, they 

 become visible as bright luminous objects against a dark back- 

 ground. Cells stained with fluorochromes absorb the ultraviolet 

 rays of short wavelength, and emit this energy in the form of 

 fluorescent light in the visible spectrum. Basic and acidic fluoro- 

 chromes act specifically to stain certain cellular structures as do 

 the more common microscopic stains such as, for instance, 

 methylene blue and eosin. The colour and the intensity of 

 fluorescence depends on the relative basophilia and acidophilia of 

 the individual cells, and upon the nature of the particular fluoro- 

 chrome. 



Fluorochromy may be employed with advantage in the study of 

 living organisms: for instance, uranin, a non-toxic stain, may be 

 injected into mice and frogs and the living organs can be studied 

 without interfering with their functioning. Fluorochromy is also 

 of practical importance for the demonstration of diphtheria bacilli, 

 tubercle and leprobacilli, malaria, etc., as well as for virus research. 



Contrary to general belief, the apparatus required for fluores- 

 cence microscopy is fairly simple and inexpensive. (A special 

 microscope is not required.) The following are sufficient. 



1. B.T.H. Mazda Mercury Vapour Lamp (box type) ME 250 

 w/50/5 (or a similar lamp as stipulated by Bertalanffy, above). 



2. A simple convex lens to project the image of the lightsource 

 through a suitable blue filter to the microscope mirror. The lens 

 and light source should be encased with a black hood to prevent 

 scattering of the rays. 



3. A yellow filter which is placed in the oculars of the micro- 

 scope to prevent any harmful eff'ect of ultraviolet light to the 

 microscopist's eyes. For this purpose Ilford's minus blue Micro 4 

 is recommended. 



It is, of course, essential that fluorescence microscopical examin- 

 ations must be carried out in a darkened room to be successful. 

 It has been stated that microscope slides of special glass are 



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