With the use of rabbits as the test animals such drugs as atropine (1.5 mg/kg), pilocarpine (10 mg/kg), and acetylcholine (0.05 mg/kg) were subcutaneously injected into animal in order to observe their influences on serum protein, hematocrit value and hemoglobin content in blood, and compared these findings with those of alkylphosphate poisoning. 1. In the case of acetylcholine and atropine injections no fixed change could be observed. Consequently, it becomes somewhat dubious whether or not the action of acetylcholine is responsible for the change of serum protein in parathion poisoning. As atropine is thought to be hydrlysed rapidly in blood of rabbit, this fact may account for no change in serum as in the case of atropine injection. 2. In the case of pilocarpine administration an increase in serum total protein, albumin, hematoerit value, and hemoglobin content and a decrease in γ-globulin were observed. With an exception of no increase in the A/G ratio at the initial stage, these findings coincide well with those of parathion poisoning. This fact seams to verify that the stimulation of the parasympathetic nerves is responrible for the changes in serum protein in the case of parathion poisoning.