278 



REPORTS ON THE STATE OP SCIENCE. 

 Fig. 4 



Plotted curve of the amount of chloroform found in the blood of two cats during the 

 6rst hour of administration of chloroform at between 3 and 4 per 100 and at about 

 2 per cent, respectively as determined by densimetry. 



APPENDIX III. 



The Influence of Oxygen upon the Ancesthetic Effect of Chloroform. 

 By F. W. Hewitt, M.A., M.D., and A. D. Waller, M.D., F.R.S. 



The ill-effects of chloroform sometimes encountered in practice, 

 referable to a state of sub-oxygenation, and the considerable 

 measure of success that the Eoth-Drager apparatus 1 has met with 

 in Germany, as well as the definite evidence of the beneficial effect 

 of oxygen inhalation that has been brought forward by Leonard 

 Hill, have induced us to make careful experiments under strict labora- 

 tory conditions as to the comparative effects of chloroform with de- 

 ficiency and with excess of oxygen in the diluent air. 



The first condition necessary — i.e., an unlimited supply of chloro- 

 form vapour of definitely known constant percentage, whether in air 

 or in air plus or minus a given proportion of oxygen — is fulfilled by the 

 chloroform balance far more effectively and conveniently than is possible 

 in any other manner. The slight correction of graduation rendered 

 necessary by the fact that the density of mixture is slightly altered by 

 the variation of oxygen is easily corrected by means of a light rider on 

 the counterpoise side of the beam. 



This automatic correction of zero requires no calculation, and the 

 correction within the scale itself is practically negligible. With the 

 three mixtures we have employed — viz., oxygen 7 per cent., 21 per cent., 

 and 97 per cent. — the weight-differences at the two extremes do not 

 exceed \ per 1,000 and 1 per 100 respectively. 



The great advantage of possessing this guarantee of the constancy of 

 chloroform percentage during prolonged experiments, as compared with 

 the insecurity offered by any fixed instrumental graduation, or even by 

 limited volumes of mixture occasionally sampled more or less accurately 



1 The delivery of this apparatus was examined and reported on, six years ago, by 

 Dr. Waller. British Medical Journal, December 24, 1904. p. 1687. 



