In 1905 I first presented my apparatus for vapor anesthesia to the medical profession. At that time it seemed quite complicated. It consisted of three bottles connected by tubing, one of which was for ether, one for chloroform and the other being a bottle containing hot water or hot neutral oil for warming the vapor, and having a tube through which the vapor was delivered to the patient. Each bottle was provided with a stop-cock, and a mixture of chloroform and ether could be given. The ether bottle contained a drum for assisting in vaporizing the ether. I have perfected the different parts and now present a simplified apparatus consisting of three bottles with one stop-cock. The drum in the ether bottle has been modified (as suggested by Dr. Charles E. Boys, Kalamazoo, Mich.), so that it now vaporizes all of the ether, and it does not necessitate refilling the bottle as often as before.