216 



PHASE MICROSCOPY IN BIOLOGY AND MEDICINE 



of Chapter VI). Other surfaces can be examined indirectly with the 

 ordinary phase microscope by first preparing a repHca of the surface 

 (Section 3.1 of Chapter IV). Large specimens like fossils, teeth, etc., 

 can be polished and thick cellulosic replicas obtained. Thinner and 

 more delicate living materials require a thinner membrane technic 

 like that used by Wolf (1948) and by Fishbein (1950). Considerable 

 detail may be seen, and such study is often helpful before turning to the 

 higher resolution of the electron microscope for finer detail. Keplicas of 



Fig. V.8. Replica from fossil wood, 135 X. A, brightfield. B-D, phase 



photomicrographs . 



fish scales should show more detail by phase microscopy. The study of 

 hair will be considered later (Section 10 of Chapter VI). 



A cellulose acetate replica of a polished piece of fossil wood obtained 

 through the courtesy of Dr. H. N. Andrews from the Missouri Botanical 

 Garden is shown in Fig. V.8. Brightfield shows detail due to the 

 adherence of microscopic bits of the rock. The pigmented parts show 

 better with the IB — 0.25X diffraction plate, and the cellular details 

 appear dark with the A+ and bright with the A— diffraction plates 

 because the material of the replica was of lesser refractive index than the 

 Clarite mounting medium. The woody structure is quite clear. Fur- 

 ther polishing and making of replicas will make serial sectioning possible, 

 and the detail can be kept by the replicas even though the original 

 specimen is destroyed by the preparation method. 



