CHLOROFORM A POISON 25 



II. The Percentage of Chloroform inhaled 



It has already been pointed out that a knowledge of the 

 concentration of the chloroform administered affords a great 

 safeguard to the anaesthetist. Such a knowledge can only be 

 obtained by the use of a thoroughly reliable apparatus. The 

 essentials, in the writer's opinion, of such an apparatus are 

 given below. 



(1) The delivery of the anaesthetic quite independently of 

 the patient's respirations, so that no variation of concentra- 

 tion will occur with variations in depth or in frequency of 

 respirations. 



(2) The nominal concentrations should under no possible 

 circumstances vary more than very slightly from the actual. 



(3) The delivery of a large enough stream of the mixture 

 to prevent the deepest respirations of the patient becoming 

 mixed with room air. (If such an event occurs, deep respirations 

 will contain a lower concentration than shallow respirations.) 



(4) An easy method of altering the concentrations. 



(5) Simplicity of mechanism and ease of portability, so far, 

 but only so far, as these may be consistent with accuracy. 



It will be seen that the writer does not favour any method 

 which depends on the patient sucking air over chloroform. He 

 bases his objection on the fact that such a method tends to 

 deliver a stronger concentration of chloroform when from any 

 reason the breathing becomes weaker. He is, however, well 

 aware of the extreme ingenuity that has been brought into play 

 to overcome this difficulty ; but he regards the difficulty as being 

 a needless one, since in methods depending on the pumping of 

 a mixture of chloroform and air into a mask the difficulty is 

 non-existent. 



A list of the apparatus of modern times for the delivery of 

 known percentages of chloroform might be usefully added 

 here. 



(1) The Dubois Pump. 



The percentage administered is in no way dependent 

 on patient's respirations. 



(2) The Vernon Harcourt Apparatus. 



This is an apparatus in which the patient sucks air over 

 a surface of chloroform (Proc. of Royal Soc, vol. lxx.. 

 p. 504, 1903). 



