SECTION TWO 



Haemorrhagic smears, therefore, present no obstacle in this 

 technique because erythrocytes appear transparent and one is 

 able, therefore, to " see through " them as if they were not 

 present. 



(/) The screening time for the experienced technician is about 

 three minutes per slide. Relatively inexperienced workers may 

 require five minutes or even longer. The screening time also 

 depends upon the size of the coverslip and the magnification 

 used. Thus, using the normal procedure including fixation, a 

 diagnosis can be made within about twenty minutes after a sample 

 has been collected. Only ten minutes or less is required for the 

 rapid procedure, however. 



References : 



Bertalanffy, F. D. (1960a, 19606). 



Bertalanffy, L. von & Bertalanffy, F. D. (i960). 



(m) The following general notes on fluorescence microscopy 

 are given by E. Gurr (195 16, 1953, 1956): 



Fluorescence is the property possessed by many substances of 

 converting short wavelengths of light into longer wavelengths. In 

 microscopy the substances and structures of most interest are 

 those which convert ultraviolet light into light of the visible spec- 

 trum, as only substances of this character can be observed directly. 

 It is, of course, well known that most living organisms are pro- 

 foundly affected by short light waves, and a great deal of infor- 

 mation as to their structure has been obtained by the study 

 of the appearance of these organisms under the influence of 

 invisible light rays. If individual cells or structural units are 

 examined before, during, and after ultraviolet treatment, enough 

 of this effect should be discovered to impart some under- 

 standing as to the changes which occur in the animal, or plant, 

 as a whole. 



In fluorescence microscopy structural details are rendered 

 visible by: (a) innate auto-fluorescence, a property possessed by 

 most tissues which when excited by short light waves become 

 clearly visible since they become luminous and glow or " fluor- 

 esce " with a radiance of their own, or by {b) secondary fluorescence 

 which is known as " fluorochromy " and is brought about by the 

 process of treatment of the tissues with fluorescent dyes and cer- 

 tain alkaloids (e.g. Berberine sulphate) and other substances. 



lOI 



