A Cell Compressor for the Measurement of Mass and Concentration by Interference Microscopy

Abstract

FOR a number of observations with the interference microscope on suspensions of living cells, it is desirable to be able to make the upper and lower surfaces of the cell flat and parallel without producing irreversible damage. A number of compressors are known (for example, Rousselet), but none provides quite the degree of control which is required. The compressor illustrated in Fig. 1 depends upon the bending of the slide S ₂ and is therefore completely free from shear play and other uncontrollable movements, unlike compressors which depend upon sliding motion. In addition, the mounting of the cells on the small strip of glass B, which is sealed to the lower slide S ₂ with ‘Araldite’, avoids any disturbances due to changes in capillary attraction. The curvature of the meniscus at M is little affected by small changes in the gap G. These two conditions enable quite reversible changes in the gap to be effected over distances of about two microns. The actual thickness of the gap can be readily measured on the microscope with the help of an air bubble as previously described¹. In addition, the medium surrounding the cells can be easily exchanged in this compressor without producing capillary disturbance.