Refractile

As the colony increases, the granular character becomes more marked, until it seems to be made up of highly refractile granules, like a mass of particles of glass.

Stained bacilli, when examined with the polarising microscope, often show a doubly refractile cell wall (e. g., B. tuberculosis and B. anthracis).

The number of refractile, ovoid spores was determined by phase-contrast microscopy using a hemocytometer.

He watched daily through the microscope for characteristic signs of viral infection, and eventually saw what he later described as a “peculiar rounding of scattered cells with refractile bodies in the cytoplasm and nucleus.”