This method is only suitable for the opening of small abscesses and other procedures requiring a very short anæsthesia. The anæsthesia is very imperfect, and only lasts for a few seconds. Many patients appear to have as much pain with this form of anæsthesia as without it. APPENDIX I. SOME EXPERIMENTAL OBSERVATIONS BY THE AUTHOR UPON THE PHYSICAL FACTS OF ETHER EVAPORATION. The apparatus was very simple. It consisted of a pump which would propel air towards the ether bottle; a glass bottle containing ether, the roof of which was pierced by two tubes, one of which carried the air from pump to bottle, and the other from bottle to a Waller’s tube, where it was collected. The percentage of ether in the air was then estimated by Waller’s gravimetric method. The ether jar stood in a water bath which could be either left otherwise empty or filled up with water of known temperature. The following tables show some of the results. In each case, the air was propelled for five minutes, by which time the cooling effect upon the ether was very marked; the figures given are averages taken from several observations. TABLE A. AIR BLOWING OVER SURFACE OF ETHER. +---------------------+----------------+----------+--------------+----------+ | Temperature of | Quantity of | Rate | Temperature | | | Bath (Fahr.) | ether before | of | of ether |Percentage| | before experiment. |experiment. | pump. |(Fahr.) at end|obtained. | | | | |of experiment.| | +---------------------+----------------+----------+--------------+----------+ | 75 | 100 c.c. | 30 | 50 F. | 12·7 | | 85 | 100 c.c. | 30 | 52 F. | 12·8 | | 75 | 100 c.c. | 90 | 45 F. | 8·7 | | 85 | 100 c.c. | 90 | 45 F. | 8·8 | | No water in bath | 100 c.c. | 30 | 32 F. | 8·2 | | No water in bath | 100 c.c. | 90 | 23 F. | 5·4 | | No water in bath | 200 c.c. | 30 | 38 F. | 9·6 | | No water in bath | 200 c.c. | 90 | 29 F. | 6·6 | +---------------------+----------------+----------+--------------+----------+ TABLE B. Showing increased percentage obtained by “bubbling through” instead of “blowing over” ether-- WATER BATH AT 75° FAHR. Quantity of ether. Rate of pump. 100 c.c. 30 Air blown over surface of ether gave percentage of ether 12·8 Air bubbled _through_ ether 23·8 TABLE C.