Abstract
Simultaneous venous and arterial blood samples were taken under varying conditions during anaesthesia and operation, and their carbon dioxide tensions were measured. From the results of 146 pairs of samples it was found that it is possible to obtain “arterialized” venous blood from the back of the hand, the carbon dioxide tension of which was the same as or very close to that of arterial blood taken at the same time. Some of the conditions needed for this arterialization were determined and observations made on certain of the factors which may impair this.