CHLOROFORM IN USE 563 



ment {e.g. from between 65 and yo° F.) will indicate a greater 

 correction at a high percentage, which is what is required from 

 the construction of the apparatus. The scale could there- 

 fore be constructed to give a theoretically perfect correction. 

 As a matter of fact the correction in the apparatus was within 

 "i per cent, of the truth between "5 per cent, and 3 per cent; 

 above and below these limits the error was a little greater than 

 this ('2 per cent.), but, as the temperature correction for these 

 extreme percentages is seldom required in practice, the elimina- 

 tion of this error was left for a future occasion. 



From all these considerations, and others that will appear 

 later, it is reasonable to conclude that the patients anaesthetised 

 with the aid of this apparatus have had the actual percentage 

 administered to them that was shown on the graduation of the 

 instrument. This may seem to the scientific mind a truism, but 

 in this the scientific mind would reason incorrectly, as the- 

 behaviour of a machine in the operating-theatre is too often not 

 that which had been anticipated by the designers. 



The Chloroform Curve 



The next step in the problem is to determine with what 

 percentage the anaesthesia is to be carried out. Obviously, it is 

 not sufficient merely to know what percentage is being given ; 

 the known percentage must also be the correct one, and, before 

 this can be ascertained on the patient, there are several points 

 to be considered, which may be briefly summarised in this 

 place. 



I. The percentage to be inhaled must not be above 2 per 

 cent, at the beginning, else there will be coughing from the 

 action of the concentrated vapour on the glottis.. 



II. Waller has shown that in animals a percentage much over 

 2 per cent, is directly dangerous. 



III. Brodie and Widdows (11) state that the most rapid 

 absorption of chloroform is to be found in the second minute of 

 anaesthesia. 



IV. Buckmaster and Gardner (8) find that there is a definite 

 danger-point in the first few minutes of anaesthesia, due to the 

 rapid rise of the chloroform contained in the blood. 



V. Embley (12) points out very clearly the mechanism by 

 means of which such danger arises. 



