392 



Prof. B. Moore and Mr. H. E. Eoaf. 



[Apr. 12, 



high practical importance, since it is upon the relationship of this 

 vapour pressure to the concentration of the solution that the amount 

 •of anaesthetic taken up by the blood circulating through the lungs 

 depends. 



It has hitherto been taken for granted that the Dalton-Henry law 

 can be applied, and that the amount of anaesthetic taken up is strictly 

 proportional to, and varies directly with, the percentage of the vapour 

 of the anaesthetic in the inspired air. 



This has never, however, to our knowledge, been experimentally 

 tested, and it seemed to us desirable to attempt such a determination. 

 We have investigated from this point of view solutions of chloroform 

 in serum, haemoglobin solution (of equal strength in haemoglobin to 

 the blood from which the haemoglobin was prepared) and whipped 

 blood, and have contrasted the pressures obtained with those of 

 solutions in chloroform, in water, and normal saline at equal concen- 

 trations. 



The vapour pressures have been measured corresponding to concen- 

 trations ranging from considerably below the anaesthetising values for 

 chloroform vapour pressure in air (viz., 8 — 10 mm.) observed by 

 Paul Bert, up to the saturation points in most cases. 



Apparatus. 



The instrument employed for this purpose was a form of 

 " differential densimeter," which, after passing through many modi- 

 fications, took the form represented in the accompanying sketch 

 (fig. 1), which is drawn approximately to a scale of \. 



The two tubes shown are exactly similar, and are graduated in 

 cubic centimetres and tenths in the upper portion, and in centimetres 

 in the lower and wider portion. 



The tubes are connected as shown by "means of thick- walled rubber 

 tubing and a glass Y-piece to a stout glass mercury receiver capable of 

 holding more than enough mercury to fill both tubes and their 

 connections. 



The tubes are held in a vertical position by clamps attached to the 

 strong vertical iron bar of a massive retort stand, and each tube is 

 capable of being moved in its clamp vertically up and down for 

 purposes of adjusting the mercury levels. 



In order to keep a constant temperature (in the case of the 

 experiments carried out at body temperature) the upper portion of 

 each tube, from about the middle of the wide part to the level of the 

 stopper at the top, was encased in a hot- water jacket of the form 

 shown in detail in fig. 2, and omitted for clearness from fig. 1. 



It was found convenient to use for the outer glass tubing of this 

 jacket the largest size of a common variety of paraffin-lamp chimney, 



