1902.] Regulation of the Administration of Chloroform. 509 



of the patient might be observed together. The second apparatus is 

 the result of an attempt to accomplish these objects (fig. 8). 



The limitation of the maximum amount of chloro- 

 form is effected by restricting the area from which 

 evaporation takes place, all the air required for 

 respiration being drawn through a small two-necked 

 bottle half-filled with chloroform. It might be 

 thought that in this case the percentage of chloro- 

 form mixing with the air would vary greatly with 

 the rate of passage of the air. But this is not so. 

 When air enters rather slowly it passes down one 

 neck and across to the other over the surface of the 

 more saturated air with only partial admixture. 

 When air is drawn through in larger volume it blows 

 down through the neck and stirs up and mixes with 

 the vapour beneath, promoting evaporation, and by 

 this means compensating for the greater dilution. 

 Thus with this apparatus also, using a bottle about 

 3 cni. in diameter, and maintaining a temperature 

 of 16° — 18°, the maximum amount of chloroform 

 is about 2 per cent. Further dilution with air to 

 reduce this percentage is obtained by the use of a Fig-. 8. 

 stopcock similar to that already described. The tem- 

 perature of the chloroform is observed by means of two specific-gravity 

 bulbs, which are in neutral equilibrium in chloroform at 16° and 18° 

 respectively. When one of these bulbs has sunk, and the other is 

 floating, the temperature of the chloroform is between 16° and 18°, 

 a variation of temperature which, it is thought, will not make a 

 material difference. By evaporation the temperature falls, and it 

 can be restored by dipping the bottle for a few moments in warm 

 water. In this case also the readings of divisions on the arc represent 

 approximately the percentage of chloroform which is being administered 

 at any moment. 



The apparatus is provided with three valves, the movement of 

 which supplies information as trustworthy as readings of the stop- 

 cock. The upper valve gives passage to all expired air, and from its 

 movement are seen the fulness and frequency of respiration. The 

 height to which the valve connected with the bottle of chloroform 

 rises shows how much air with 2 per cent, of chloroform is being 

 inhaled ; the height to which the valve admitting pure air rises 

 shows to what extent the mixture of air and chloroform is being 

 diluted with pure air. For example, when the pointer is in the middle 

 of the arc the two valves rise equally, showing that the original dose 

 is being diluted with an equal volume of air, or that there is being 

 administered air containing 1 per cent, of chloroform. 



