ON ANESTHETICS. 



273 



through both bottles in series. The reason for this is the rapid lowering 

 of temperature due to rapid evaporation. For the same reason the 

 bottles are surrounded by a warm water-jacket. In this form the 

 apparatus has proved to be capable of affording a continuous stream 

 of ether-and-air at percentages from 8 to 24 at the rate of 5 to 10 

 litres per minute — i.e., sufficient for laboratory purposes, and in all 

 probability sufficient for clinical use. The supply of ether vapour at 

 known and controllable percentage is ample for anaBsthesia in the 

 laboratory, and sufficient to demonstrate there the fatal effects of over- 

 dose by ether in comparison with overdosage by chloroform. In this 

 particular the effect of a 24 per cent, ether mixture is approximately 

 equal to that of a 3 per cent, chloroform mixture. But clinically 

 employed there is little chance of overdosage by ether, of which the 

 characteristic advantage, and drawback, is that it can be used as clumsily 

 as possible with little risk of misadventure other than an imperfect 



Units per cent, indioated by a given bulb on a chloroform scale are to be 

 doubled if the bulb is used to indioate ether percentage. 



Time In Mtns 



Fig. 1. — Graphic record of the chloroform percentage at which anaesthesia was 

 induced. The anaesthesia was complete at the end of 11 minutes at slightly 

 above 3 per cent. The percentage was then reduced in steps to 2 per cent., 1 per 

 cent., and below. Subsequently anaesthesia was maintained at about this per- 

 centage for six hours. 



J l_ 



J I 1_ 



J L. 



_1 l_ 



_1 I 



Time in Mini 



'0 



15 



20 



25 



30 



«0.2. — Graphic record of the ether percentage at which anaesthesia was produced. 

 The percentage of ether was raised in three steps to 8, 16, and 24 per cent. 

 Anaesthesia was complete at the end of 15 minutes at the point marked |. The 

 percentage was maintained at 24 for a further 10 minutes to the point marked * 

 when respiration ceased and the balance-case was opened so that the indicator 

 fell to zero. 



The chloroform scale 1, 2, 3 per cent, is at the same time an "ether scale 

 2, 4, 6 per cent. But since we require for ether a scale indicating up to a value of 

 20 to 25 per cent., it is convenient to use a smaller bulb for ether than for chloroform 

 to obtain indications within such a wide range. Obviously, halving the vohnre of 



