ON ANESTHETICS. 



165 



This example shows that the maximum percentage afforded by ' open 

 ether ' with a closed face-piece is approximately 20 per cent., falling 

 by reason of evaporation and cooling. It illustrates further that for 

 these measurements we may take direct scale-readings without 

 troubling to get out corrected figures. 



According to my previous observations, this ether value of 20 per 

 cent, is physiologically equivalent to the chloroform value of 2'5 per 

 cent. 



Observation 2a. — Same arrangement as in Observation 1, but no 

 valve on the tracheal tube, so that both inspiration and expiration 

 occurred from and to the face-piece. Temp. =22° ; bar. =760 mm. Hg. 



Observation 2b. 

 30° C.: — 



-The same, but with all apparatus warmed up to 



Observation 3. — With Sir Frederic Hewitt, to imitate as closely 

 as possible actual procedure: — 



An attempt to raise the percentage above 12 by excess of ether 

 did not succeed, i.e., there is no liability to danger by accidentally 

 exceeding the natural maximum percentage. 



The current phrase ' open ether ' is used, I understand, in opposition 

 to ' closed ether ' administered from a bag such as Clover's, but does 

 not exclude the use of a Skinner mask brought into close apposition 

 with the face, in which case the ' opening ' consists of the pores of the 

 fabric. The essential point which is held to be secured by such an 

 ' open method ' with closed mask is that the patient is not made to 

 breathe and rebreathe the same mixture of air, ether, and accumulating 

 carbon dioxide. The ' open ether ' method is substantially identical 

 with the method that was shown to me in 1898 at the Massachusetts 

 General Hospital as the regular method there practised since 1850, 

 i.e., the mask kept saturated with ether is gradually brought closer 

 and closer to the face to give a gradually increasing percentage, until 

 finally it is quite closely applied, so as to give the maximum percentage. 

 It would, I think, be a suitable recognition of the pioneer work in ether 



