PREPARATION METHODS 173 



The standard phase microscope condenser is made for normal micro- 

 scope shdes 1.15 to 1.25 mm thick. Very thin slides may cause the oil 

 contact to break between the slide and the condenser when the con- 

 denser is properly focused. This may be avoided by applying a more 

 viscous immersion oil (e.g., Shillaber's Heavy) or by oiling a piece of 

 cover glass to the top of the condenser. 



For examination of thicker mounts two alternatives are possible. 

 About 3 mm of the top lens of the condenser may be removed to allow 

 the use of preparations up to that much thicker. For deeper mounts 

 the top lens is removed from the condenser and an annulus for long focus 

 is used. With a l(3-mm objective a condenser working distance of 

 about 18 mm is possible, and Carrel and roller tubes can be examined. 

 Only the region of the top of the roller tube can be studied, as the 

 curvature of the tube elsewhere prevents proper adjustment of the 

 phase system. For 4-mm objectives the top lens of the condenser is 

 replaced with that from a N.A. 0.66 condenser. The working distance 

 is somewhat less at these magnifications. With such systems, frequent 

 checking with the telescope is necessary to make sure that the annulus 

 and the diffraction plate are concentric in order to obtain efficient phase 

 microscopy. Moving the preparation usually necessitates recentering 

 of the phase system. The above description applies to the Spencer 

 equipment. A long-focus condenser with different lenses and annuli 

 for longer working distances is also available from Bausch and Lomb 

 Optical Co. 



It is essential that the proper combination of annulus and objective 

 be used, which is readily determined by noting whether thejmage of 

 the annulus and diffraction plate superimpose when examined with the 

 telescope. When the specimen is too dense, it may be mo^'ed to one 

 side, and the checking done. A wedge effect will lessen the effectiveness 

 of this substitute procedure, but adjustment may be made until the 

 contrast is optimal as the specimen is watched. For best results the 

 lamp iris should be focused with the microscope condenser onto the 

 specimen before the annulus is matched with the diffraction plate. 



Specimens of li\-ing matter should be mounted in appropriate physio- 

 logical isotonic media, such as Ringer's or Locke's solution, to avoid 

 distortion. Dalton et al. (1949) recommend cold 0.88 M sucrose, 

 especially when the material will be examined later with the electron 

 microscope. Albertini (1948) proposes the following solution, which he 

 calls Tyrofusine KA, for histological and neoplastic cells: Na3P04 0.05 

 gram, NaHCOs 5 grams, NaCl 85 grams, KCl, 4.2 grams, CaCl2 2.5 

 grams, MgCl2 0.05 gram, pure glucose 10 grams, HOH to 10 liters. 

 This is sterilized for 1 hour with steam on successive days. 



