The actual state of things was clarified in the 1st chapter, by having taken investigations in so numerous pathological cases as 43, along with plenty of animal tests. Then, intaking consideration for the present importance of parathion poisoning, the virtue of certain medical compounds for this poisoning especially important for clinies was examined systematically and at the same time, certain fixed criteria for treatment reduced from those tested cases was determined; above all, some standards for use of atropin was established. 1. By administering some medical compounds mainly thought effective towards autonomous nervous system, especially anti-acetylcholin, and antidote to a mouse and rabbit poisoned by parathion, took observations on those changes that have occurred to death rate, change of blood cholinesterase and other symptoms. 2. On examination by animal tests, upon the effeets indicated by Atropin, Finalin, T.E.A.B., Banthine, Glucuron acid, Sodium thiosulfate and B.A.L., toward parathion-poisoning, found out atropin as best, B.A.L. next; while, certain merit could be proved by sodium thiosulfate and Finalin. 3. Atropin seems to give slightly felt effect on the cholinesterase inhibitoy function caused by parathion. 4. From those results obtained in treating by atropin many cases of parathion-poisoning patients 10 of which looked serious, superiority of a large dose of atropin was recognized, and then I established certain criterion of atropine treatment on parathion-poisoning.