ORIENTATION 193 



optimal \4sibility from a series of diffraction plates of different contrasts 

 and kinds, and the possibilities of phase microscopy with tissue cultures, 

 microorganisms, fibers, surfaces, emulsions, homogenization of milk, 

 and foods. The use of the phase microscope in bacteriology was dis- 

 cussed by Knoll (1944) including the saving to be gained from the 

 elimination of staining procedures. 



In 1945 a bacteriophage was seen and studied with the phase micro- 

 scope by Hofer and Richards. Albertini (1945) discussed the impor- 

 tance of phase microscopy with fresh material, exudates, and frozen 

 sections, and its applications in tumor diagnosis. Vital staining is 

 aided with phase (Frauchiger, 1946), and Harrison et al. (1946) re- 

 ported phase helpful in the study of serological reactions with protozoa 

 and documented their results with a motion picture. Surface patterns 

 of epithelial cells were seen by Albertini (1946a) and independently 

 discovered by Ralph (1947). These patterns resembled the ridges 

 of fingerprints. 



The use of the Spencer phase microscope for some sixty specimens, 

 its use with replicas for the study of surfaces, the combination of color 

 and phase contrast, and the advantages of an optical equivalent of 

 differential staining achieved by means of several different contrasts 

 with the same specimen were described by Bennett et al. (1946). The 

 clear detail revealed in emulsions and in living organisms was blurred 

 by Brownian movement and movements of the specimen until Richards, 

 in 1945, with an electronic flash produced photomicrographs sharp 

 enough for measurement. A long-focus condenser was devised so that 

 such studies could be made of cultures in Petri dishes, Carrel flasks, 

 and other containers thicker than the microscope slide (Richards, 

 1946a, 1947a). 



General articles by Taylor (1946), Martin (1947), Barer (1947, 

 19485), and Magliozzi (1948) added applications with microfilaria, 

 diatoms, urine sediments, Chaoborus, Botryllus, Purkinje, and muscle 

 cells, seen with Cooke, Troughton and Simms and with Bausch and Lomb 

 phase microscopes (dark A— contrast). Richards (1947c) reviewed 

 biological phase microscopy. Most of the British and European 

 contributions were made with dark-contrast (A — ) eciuipment by 

 Cooke, Troughton and Simms and by Zeiss, whereas the greater number 

 in America have used Spencer equipment with all contrasts. The 

 possibilities of phase microscopy in biology and medicine were by then 

 reasonably clear, and the publications were becoming concerned more 

 with the phase microscope as a means of solving problems. These 

 contributions will be included in a systematic examination of the 

 various fields of microscopy in the rest of this chapter. 



