The changes of dislocation arrangements and latent image distribution in tabular silver bromide crystals in gelatin matrix were observed after deformation by an electron microscope at low temperature. Majority of original crystals were found free from dislocations. Dislocations were introduced by the application of pressure. These dislocation lines provided the centers of development. The surface latent image did not form in the dislocation-induced crystals. The crystals deformed exclusively cracked along [110] or [211] directions. The formation of latent image specks seemed to occur most readily at those cleavage cracks. The increase or decrease in sensitivity of photographic emulsion by application of pressure might depend upon whether the cleavage cracks were formed on crystal surfaces or not.