SECTION FIVE 



of sediment which is then well mixed with a drop of paraffin oil 

 and covered with a coverslip before examination with the oil 

 immersion lens. 



(a) For bacterial counts: 



A loopful of the stained and shaken soil suspension is placed 

 on a slide, covered with a coverslip, and examined with an oil 

 immersion lens. A counter of 20/x depth combined with a 

 counting ruled eyepiece is used. The particles of soil covered 

 with humus and the particles of humus slime show a dim red 

 fluorescence and the living bacteria are green. The stained 

 bacteria are not killed and may be used for culturing. 



To diff"erentiate between living and dead cells, solution G 

 should be used: living cytoplasm and nuclei show green fluor- 

 escence, whilst dead protoplasm develops a bright copper- 

 coloured fluorescence. 



Reference: Strugger, S. (1948), Canad.J. Res. Sec. C, 26, pp. 188-93. 



7. Vital Staining of Living Trypanosomes in Blood 

 (S. Strugger 's Method) 



Solution required: 



Acridine orange o-oi% in 0-85% 

 sodium chloride. 



Technique: 



1. A drop of blood suspected of containing trypanosomes is 

 mixed on a slide with a few drops of the acridine orange solution, 

 and covered with a coverslip. 



2. Examine with a blue light fluorescence microscope, which 

 may be constructed as follows : parallel rays produced by attach- 

 ing a convex lens to the lamp are filtered with a curvette (2 J cm. 

 thick) filled with saturated solution of copper oxide ammonia so 

 that only the blue light reaches the plane mirror of the microscope. 

 A filter containing an orange glass which absorbs blue light 

 quantitatively, but allows green, yellow and red to pass unchanged, 

 is placed over the ocular. A slide with powdered anthracene in 

 liquid paraffin is used for focusing. 



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