The tissue cholinesterase (ChE) activity in normal rabbit was the highest in the central nervous system, and was high following descending order; liver, spleen, erythrocyte, lung, serum, gastrointestinal tract, kidney, heart and muscle.
By a subcutaneous parathion injection, there occured the changes of ChE both in the tissues and blood as follows. 1) At the time of death caused by the administration of 100 mg/kg of parathion, the ChE in serum, erythrocyte and central nervous system were inhibited strongly than that in the others and the inhibition of liver ChE was the slightest. 2) On the case of the administration of 5 mg/kg of parathion, the inhibition of ChE was great in blood, slight in the liver and moderate in the central nervous system. On this case, the inhibition of ChE in the tissue was maximum after 6-12 hours, and the restoration of it was after 11 days, but in the kidney both were slower than the others.