PRESIDENTIAL ADDRESS. bo'.) 



attempt to assign a definite meaning to every incident of structure. That this 

 attempt should be limited by precise thinking goes without saying, and I may 

 be allowed the hope that my transgression outside the realms of precision have 

 not been beyond the tolerance of this Section of the British Association for the 

 Advancement of Science. 



The following Reports and Paper were then read : — 



1. Third Interim Report on Anaesthetics.- — See Reports, p. 154. 



2. Additions to the Use of a Chloroform Inhaler. 

 By Dr. A. G. Vernon Harcourt, F.R.S. 



In a report to this Section two years ago the Committee on Anaesthetics 

 ' deprecate the use of apparatus based on the vacuum principle,' and ' consider 

 it essention to any form of apparatus that it should be based on the plenum 

 principle, by which an excess of anaesthetic vapour suitably diluted with air is 

 propelled to an open mask by mechanical means.' 



The distinction may be illustrated by an inhaler ' based on the vacuum prin- 

 ciple,' which has been used in many thousand cases during the past ten years, and 

 by the same instrument with an addition made more recently fitting it for use 

 on the plenum principle. The addition consists of a forked three-way tube, of 

 which one branch is connected with a bellows and the other two with the 

 chloroform bottle and the air-inlet respectively. 



As nearly as may be, the strokes of the bellows, which delivers about 500 c cm. 

 at each stroke, should be made to coincide with the in-breathings of the patient. 

 When the operation would not be interfered with by a mask covering mouth and 

 nose, a loose mask may be used, and in the opposite case tubes entering mouth 

 or nostrils only. 



By the use of bellows the information which the valves give as to the fre- 

 quency and strength of a patient's breathing is lost, and the working of bellows 

 makes an additional demand upon attention. Those who have trusted to the 

 breathing of a patient when administering chloroform through a mask may wish 

 to do so still. They will be less deterred from doing so by the adverse verdict 

 of the Committee if they examine the 'First Experiment' quoted as 'sufficiently 

 illustrating the ease ' with which dyspnoea can be produced in the human subject 

 by slight obstruction. They will find that the cause of the dyspnoea was the 

 broad 1-inch tube, not by its obstruction, which as compared with that of the 

 nostrils is indeed slight, but by its capacity, which makes the total dead-space 

 exceed the volume of respiration, so that the expired air, with but little addition 

 of fresh air, was breathed again and again. Had the customary half-inch tube 

 been used, the obstruction would have been greater, but the additional dead-space 

 only one-quarter as great, and there would have been no dyspnoea. 



The second addition is that of an oxygen-bottle connecting through a valve 

 with a conical reservoir of about 250 c.cm. capacity. The outlet of the reservoir 

 connects with the chloroform bottle and the air-inlet. For use, the tap of the 

 oxygen-bottle is turned on till the valve through which the oxygen passes is lifted 

 at the end 2 or 3 mm. above its seating. Oxygen is then entering the reservoir at 

 about half the ordinary rate of inspiration. This continues during expiration, at 

 the end of which period the reservoir is nearly full of oxygen mixed with some 

 air. During the following similar period of inspiration the oxygen flowing from 

 the bottle is inspired together with that in the reservoir; after which the process 

 repeats itself. With oxygen as with air a dose of chloroform may be given 

 which is immediately variable at will from to 2 per cent. The reservoir pre- 

 vents the waste, otherwise unavoidable, of more than half the oxygen. 



The third addition to the use of the inhaler is to use the same apparatus for 

 administering oxygen only. For this purpose water, kept warm by the night- 

 light below, would take the place of chloroform, and the pointer on the arc 

 would be so turned that the air-inlet was closed and all that was inhaled passed 



