18G 



Dr. Buchanan on the Effect* of the Inhalation of Ether. 



the remainder too highly rarified to be respired without danger of 

 asphyxia. In cold weather again, the apparatus must be maintained by 

 artificial heat at G0°, for it is only by a scrupulous attention to the 

 influence of temperature, that the time of inhalation of the ether can be 

 rendered a measure of its physiological effect. 



The reason why the chamber of the instrument should be large has 

 been already pointed out. The larger it is the more complete will be the 

 uniformity between the successive quantities of ether drawn into the lungs 

 at each inspiration. It should probably not be of less capacity than from 

 1300 to 1400 cubic inches, the volume of air consumed by respiration in 

 five minutes. A cubic foot is a simpler measure, and, if adopted as a 

 minimum standard for the size of the chamber, would render all observa- 

 tions made with instruments so constructed comparable with each other. 

 It is true that such an instrument will not go into the surgeon's pocket, 

 but this is probably no disadvantage, for an agent so energetic as the 

 vapour of ether should not be employed on light occasions, but only after 

 deliberate consideration. 



The tubes and apertures of the chamber should not be less than an 

 inch in diameter, for when they are narrower, especially if the tubes be 

 long, the difficulty of respiration is much increased. Care should be taken 

 to keep the apertures perfectly free, instead of choking them up as is 

 often done with sponges soaked in ether. 



The valves are a frequent source of difficulty. As they are fitted on 

 narrow apertures, they impede the respiration to a certain extent, even 

 when they are in good working order; but they are very liable to 

 derangement, and may then readily occasion asphyxia. 



Having frequently witnessed how imperfectly the valves perform their 

 office, it occurred to me that an apparatus might be constructed without 

 any valves; or, to speak more correctly, substituting for the solid valves 

 now in use, liquid valves, which require no contraction of the tubes, and, 

 from their simplicity of structure, are not liable to go out of order. The 

 principle of this contrivance will be understood by reference to fig. 1. 



Fig. l. 



