Differences were studied in detecting residues of inhibitory substances in tissue samples of pigs and calves after emergency slaughter. Samples of liver, heart, kidney and muscle of 30 pigs and 16 calves were examined. Solid samples of organ tissues placed on an agar medium and extracts of the solid samples placed into agar pits were used for detection. Samples were parallelly subjected to the microbiologic diffusion method, using the S. aureus CCM 2022 and B. subtilis CCM 1999 microorganisms. The method of obtaining the extracts from solid samples of the organs was proposed and tested at our own workplace. The presence of inhibitory substances was displayed by the formation of inhibition zones. Results of the positive samples in calves (7 samples) and in pigs (3 samples) point out explicitly to the fact that the extracts of the tissue samples display positively larger inhibition zones in comparison with the solid samples. B. subtilis was demonstrated to be more sensitive than S. aureus, comparing the used microorganisms.