The Action of Formaldehyde on Living Cells as Studied by Phase-contrast Microscopy

The morphological changes occurring when living cells are fixed in neutralized formaldehyde have been studied in detail with phase-contrast microscopy. The cells used were (1) salamander spermatogonia obtained from the teased testis, and (2) snail amoebocytes growing in tissue culture. The cells were mounted on a slide beneath a coverslip ringed with paraffin wax. Various strengths of formaldehyde made up in saline or distilled water were then introduced while the cells were kept under constant observation by phase-contrast microscopy. The morphological changes during the fixation process were observed for periods of at least 24 hours and the results recorded photographically.