210 PHASE MICROSCOPY IN BIOLOGY AND MEDICINE 



element. Gatenby and Moussa (19-49) have studied this in dorsal root 

 ganglia. 



Thorell (1947) used the phase microscope with an auxiliary lens for 

 the measurement of cell thickness. Jones (1947c) recommends phase 

 microscopy for optical sectioning to determine in which layer of a cell 

 the inclusions are arranged. A pattern resembling the ridges of finger- 

 prints was found on the surface of epithelial cells by Albert ini (19466), 

 Baud (1947), and Ralph (1947). Bejdl (1949) interprets these as the 

 remains of intercellular bridges, as did Chambers and de Renyi (1925). 

 Richards (1949r/) exibited phase stereophotomicrographs of these ridges 

 and of various kinds of cells showing the three-dimensional distribution 

 of cellular content of nerve fibers and capillaries in tissues. Nissl bodies 

 have been studied by Hoessley (1947) and Albertini (1948) (see also 

 Section 6). Cellular details seen with phase and ultraviolet micros- 

 copy have been compared by Ludford et al. (1948). Dedifferentiation 

 of cells has been reported by Albertini (194()6). 



Details may be seen in tissue sections (Fig. V.()) when the section is 

 not too thick. If the material is embedded in paraffin it is necessary 

 to remove it before examination (see also Fig. VI.l ). Albumen embed- 

 ding proposed by Wilson (1942) should be useful in phase microscopy. 



A most impressive application of the phase microscope for the elucida- 

 tion of cellular structure and behavior is seen in the motion pictures of 

 Michel (1941), Firor and Gey (1947), Fell and Hughes (1949), Hughes 

 and Preston (1949), and Hughes and Swann (1948). The changes in 

 the chromatin as the chromosomes form and divide and of the cyto- 

 plasmic constituents show clearly in Michel's film. Unfortunately the 

 dark (A — ) contrast did not show the spindle fibers. Other types may 

 do so and should be tried. A film combining phase and polarization 

 microscopy in successive frames and showing both chromosomes and 

 spindle fibers is reported by Hughes and Swann (1948). Gey reports 

 special advantage from study with phase of the cell membrane during 

 division. 



5. KILLING AND FIXATION 



For many years microscopists have differed as to how well the usual 

 killing and fixing technics retain the detail of the living cell, or whether 

 artifacts are produced. The transparency of living cells prevented clear 

 observation of them by brightfield methods in most cases. Buchsbaum 

 (1947, 1948) examined salamander macrophages in living tissue cultures 

 with the phase microscope and then studied the changes after fixation 

 and staining. Photomicrographs were made for record. Acetic acid 

 containing fluids (Bouin's and Carnoy's) caused cytoplasmic distortion. 



