The cytology of a strain of Corynebacterium diphtheriae.

Organism studied. Corynebacteriunm diphtheriae, type mnitis, strain A9255. Growth media included M. and E. (AMorton and Engley, 1945) broth and agar, with and without enrichment by whole blood, plasma or the lysate from human blood cells subjected to freezing and thawing. Culture was usually at 37 C; occasionally, at room temperature. Stained preparations. Cells in broth culture were placed on agar blocks, fixed for 1 minute in the vapors of a 2 per cent aqueous solution of osmium tetroxide, partially dried, and impressed onto coverslips. Cells from agar grown cultures were smeare(l di1ectly onto coveislips and similarly fixed. Prepaiations were stained by a variety of oxidation-reduction indicators and differential stains as indicated under "Results". Mounting was usually in Farrant's (aqueous) medium or H.S.R. (Harleco Synthetic Resin). Examination was with a Bausch and Lomb research microscope with bal-coated lenses, a 15 X eyepiece (12.5 for photography), and 97 X achromatic oil immersion objective of n.a. 1.25. Photographs were taken with a Bausch and Lomb L camera. Final magnification of prints was 4,850 X. Preparations for electron microscopy. Cells were suspended in distilled water, placed on collodion films overlying agar, and dried (Hillier et al., 1948). Films bearing the cells were cut out, fixed in the vapors over 2 per cent 0$04 solution, floated in distilled water for an hour to dialyze away undesirable deposits, and picked up on 200