CHAPTER V 



PHASE MICROSCOPY IN BIOLOGY AND 



MEDICINE 



1. ORIENTATION 



The phase microscope is particularly suited to the examination of 

 cells, tissues, and organisms too transparent in their normal state to be 

 seen with other methods of microscopy. With the proper choice of 

 diffraction plates details may be seen with an optical equivalent of dif- 

 ferential staining. Sharp boundaries are provided for measurement, 

 adequate contrast for counting, with no loss of time for staining pro- 

 cedures (often important in clinical diagnosis) and with no question as to 

 how much the preparation has altered the specimen. Slight absorption 

 from small amounts of natural pigment, from failure to obtain adequate 

 staining, and in faded preparations from old collections may be made 

 visible with the phase microscope. Color contrast may be combined 

 with phase contrast when desirable. The changes due to killing and 

 fixing fluids or the effects of other chemical and physical agents may be 

 seen, watched, and assessed. Digestive processes, sol-gel transforma- 

 tions, and other variations in concentration of materials also can be 

 seen and evaluated with the aid of the phase microscope. 



Because of these advantages for the biologist, the earlier articles on the 

 phase microscope were illustrated mainly with biological specimens. 

 Kohler and Loos (1941) demonstrated that phase microscopy provides 

 greater and more useful visibility for urine sediments, blood cells, 

 epithelial cells, trypanosomes, and an unstained kidney section. Pic- 

 tures of living staphylococci, diphtheria bacteria, connective tissue, 

 fibroblasts, mouse tumor, fungus, and yeast were shown by Loos 

 (1941a, h). Michel (1941) examined the cells in the testis of Oedipoda 

 germinatica and salivary gland chromosomes and made an unusual 

 motion picture film showing sperm formation in the grasshopper. 

 Spirochetes and epithelial cells were examined by Burch and Stock 

 (1942) with a slit type rather than the annular form of diffraction plate. 

 Photomicrographs of unstained, living lactic acid bacteria, yeast, 

 Sarcina, mycelium, epithelial cells, chromosomes of Chiroriomus, 

 trypanosomes, and brain-tissue sections in dark contrast were made by 

 Bosshard (1944). Richards (1944) published pictures in bright and 

 dark contrast of epithelial cells from the frog nictitating membrane and 

 pointed out the advantage of choosing the diffraction plate giving the 



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