Glaubach and Pick1 were the first to find that procaine causes a fall of body temperature. The fall has recently been shown by Peczenik2 to be greatly increased after adrenalectomy. The work of Dawes3 in this laboratory on quinidine substitutes led him to point out that quinine, quinidine and procaine antagonize the effect of acetylcholine on many types of tissue. They reduce its effect on the heart and on the intestine, and they reduce its effect on skeletal muscle also (Harvey4). Thus procaine, in addition to being a local anaesthetic, reduces the action of acetylcholine in all forms of muscle. Recently, de Elio5 has shown in this laboratory that procaine shares these properties, not only with quinidine, but also with atropine and with the analgesic ‘‘Pethidine (demerol), while Dews and Graham6 have shown that the antihistamine substance ‘‘Neoantergan shares them too.