HISTOLOGY 213 



transmission. Cartilage shows organized structure when unstained and 

 considerably more detail after light staining with toluidin blue. The 

 IB— 0.25X phase objective is preferable for stained connective tissue. 

 Bensley (1950) has a phase picture of the intercellular substance in 

 loose connective tissue. 



Blood may be examined without staining as the phase microscope 

 shows fine detail in the leucocytes and transition cells. Hematologists 

 prefer a medium dark (A — ) diffraction plate for fresh smears, but the 

 IB— 0.25X plate shows better color contrast and detail in supravitally 

 stained blood. Brecher (1948, 1949) used phase microscopy for the 

 examination of reticulocytes, and Hoffman and Rottino (1950) discuss 

 the progressive cytolysis undergone by reticulocytes in Hodgkin's 

 disease leading to Sternberg-Reed cells. Radiation effects on blood 

 were studied by Dickie and Hempelmann (1947). Phase microscopy 

 is helpful in counting platelets in a shallow 0.05-mm hemocytometer 

 using Feissly's (1948) diluting fluid of cocaine HCl 3 grams, NaCl 0.20 

 gram, in 100 cc Aq. dest. (See also Ralph, 1950.) Jones (1947a, 6, c. 

 1948o, b) has made effective use of the phase microscope in the study of 

 blood-cell development of the rat embryo with especial reference to mi- 

 tochondria and nuclear details. Moeschlin (1949), on comparing phase 

 microscopy with the usual methods of examination of stained blood 

 smears, concluded that the former yields new information of diagnos- 

 tic importance. Bessis (1949a, h) and Bessis and Bricka (1949) have 

 published an atlas of blood-cell phase pictures. They have also com- 

 bined phase microscopy with shadowcasting technics to increase con- 

 trast. Ludin (1947, 1948, and in the discussion of Aloeschlin, 1949) has 

 found phase microscopy useful for study of motion of cells and of divid- 

 ing cells such as neuterophil leucocytes and megaloblasts. Feissly and 

 Ludin (1949) discuss hemolysis and the transformation of thrombocytes 

 as seen with phase microscopy. Bolen's method has been examined b}^ 

 Lind and Ashley (1950). Other possibilities with the phase microscope 

 for tissue structure will be discussed under pathology. Kohler and 

 Loos (1941) and Crossmon (1950) recommend phase for counting cells 

 in a hemocytometer. 



The ash from microincineration of a tissue section is distinctly more 

 visible with medium bright or low B— contrast phase objectives. 



Very transparent tissues, like the vitreous body of the eye, are seen 

 with the phase microscope to be composed of fibers, cells, and media of 

 different optical densities. Very fresh corneas show the epithelium and 

 mesothelium but little detail in between. The tissue soon deteriorates, 

 as an isosmotic mounting fluid for the epithelium is not correct for the 

 mesothelium, and then fibers and nerve cells may be seen as the tissue 



