Showing amounts of ether vaporised at varying pump rates. In each case, the temperature of the water bath was 75, and the initial amount of ether was 100 cc.-- Pump Amount of Ether Rate. Vaporised. 30 30 c.c. 90 38 c.c. These experiments justify one in drawing the following conclusions:-- 1. The effect of a water bath has a marked effect in increasing the strength of the vapour yielded, but small variations in the temperature of the bath (as between 75 and 85 Fahr.) have but little effect. 2. If ether is vaporising quickly, it cannot pick up heat from the water bath as quickly as it is losing its own heat. Though not shown in the tables, the actual loss of temperature on the water bath was small--about 2 degrees Fahr. during the five minutes experiment. 3. The more forcible the blast of air blown over or through the ether, the less the percentage of ether yielded. Table C shows that this loss of percentage is not compensated for by an increase in the total amount vaporised. Of course, these results only apply to the case of a strong current of air. If the current of air were _very_ small, the ether could pick up heat as fast as it parted with it, and within moderate degrees a little increase of the air stream would increase the total amount of ether vaporised without reducing the percentage strength. These results are of some practical importance in connection with so-called “vapour anæsthesia” as given for instance by Shipway’s instrument (page 90), and in devising and using the ether chambers of intratracheal apparatus. APPENDIX II. THE PERCENTAGE STRENGTH IN OPEN ETHER. Hewitt and Syme (_Lancet_, 27th Jan. 1912) estimated the percentage of ether obtainable from an open mask with varying materials and quantities of the drug. The results are tabulated below:-- A.--A WHOLE MASK JUST MOIST. Material stretched Number of Percentage on mask. layers. obtained. Gauze 4 11 8 11·4 12 11 Flannel 1 8·0 2 8·0 Lint 1 10·0 B.--WHOLE MASK WET. Gauze 4 12 8 13·4 12 14·0 Flannel 1 8·0 2 8·0 Lint 1 8·0 By excessive douching the observers were able to obtain 17 per cent.