Further Observations on the Spodogram of Bacillus cereus Endospore

Abstract

Endospore spodograms of B. cereus C3 were examined in dark contrast by use of the phase microscope with oil-immersion objectives. When the spodograms were mounted in air, their central part, or core, appeared bright; when mounted in water or oil, the central part appeared dark. The central part of the normal, unincinerated spore appeared bright in air and water, but dark in oil. This indicated that whether a body appears bright or dark when observed with the phase microscope does not depend only on its ref ringence relative to that of its surround, but also on its thickness and on the magnitude of the difference between its refractive index and that of its surround. Present observations showed that, contrary to a previous conclusion, mineral matter is more highly concentrated in the core than at the periphery of the endospore.