iS SCIENCE PROGRESS 



expired air will be greater than in the later stages of anaesthesia. 

 In other words, if the percentage of chloroform in the inspired 

 air be kept at the same level, the concentration of the anaesthetic 

 in the expired air will be constantly rising, and, therefore, also 

 rising in the alveolar air, in the blood, and in the lymph. The 

 conclusion is obvious, that a safe percentage to administer early 

 in anaesthesia is not necessarily safe in the later stages ; and further, 

 that the percentage of anaesthetic in the inspired air can be slowly 

 diminished without diminishing the concentration in the alveolar air, 

 for as the alveolar air loses less and less anaesthetic to the blood as 

 anaesthesia advances, the alveolar air requires less and less vapour 

 to be added to it to maintain its concentration. 



One cannot, therefore, answer the question, " What do you 

 consider a safe percentage of chloroform to administer ? " 

 without first asking, "To what period of anaesthesia do you 

 refer ? " Even on obtaining an answer to this, one is unable 

 to give a dogmatic reply, until one is aware of the amount of 

 lung ventilation that the patient may possess. This matter will 

 be considered anon. At the present stage of our investigation 

 we can declare that what is a safe percentage of chloroform to 

 administer early in anaesthesia may be a fatal percentage in the 

 later stages of narcosis. The Special Chloroform Committee of 

 the British Medical Association in 1904 reported that 2 per cent, 

 of chloroform was sufficient to induce anaesthesia in the human 

 subject, and 1 per cent, of chloroform to maintain it. This may 

 be taken as a fairly accurate statement in reference to the 

 majority of cases that require the administration of an anaesthetic. 

 But as it will be shortly pointed out that the question of lung 

 ventilation plays an important part in the rate of absorption, 

 no such statement can be of anything approaching universal 

 applicability. It must always be remembered that a vapour 

 pressure of chloroform in the lymph corresponding with a 

 2 per cent, mixture with air is certainly a fatal concentration. 

 Consequently the administration of 2 per cent, of chloroform 

 must, if continued, ultimately prove fatal, the length of time 

 intervening being proportional to the rate of absorption, which 

 rate will vary with variations in lung ventilation. 



In this connection Waller has conclusively shown that in 

 the case of cats a 2 per cent, vapour of chloroform is safe to 

 administer during the induction of anaesthesia. Yet from 

 experiments the writer has performed on the same animals he 



