ON ANASSTHETICS. 3805 
APPENDIX III. 
On the Physiological Effects of Mixed Anesthetics. 
By Dr. A. D. Watuzr, F.R.S. 
In a paper recently presented to the Royal Society’ I give in 
conclusion of a long series of experiments the following physiolo- 
gical equivalence of chloroform, ether, and alcohol: 1 ¢.c. chloroform 
=15 ¢.c. ether =75 c.c. alcohol. 
Adopting as a basis of calculation that the physiological power per 
unit of volume is therefore— 
Alcohol, F ; - 5 - ae all 
Ether . , : > - 4 - cas ib 
Chloroform , © ‘ . ‘ ° Poms) 
I proceeded to compare the effects of mixtures of anesthetics with those 
of their constituents. 
I found, in the first place, that the components of a mixture do not 
sensibly modify each other’s effects. Taking, e.g., the physiologically 
equivalent solutions— 
Alcohol. ° : ‘ . . 76 c.c. per 1000 c.c. saline 
Ether . : . . . » 16 ” ” ” ” 
Clorolorml veh we pe el 5, ” » 
I found that mixtures of these solutions produced about the same 
aneesthetic effect as did any one solution. 
Taking next a mixture composed of equal parts of ether and chloro- 
form, I found that its physiological strength was approximately one half 
that of pure chloroform, i.e., that a 2 c.c. per 1000 solution of the mix- 
ture was physiologically equivalent to a 1 c.c per 1000 solution of chloro- 
form alone. Theoretically, from the numbers given above, the equiva- 
lence should have been 1°88 c.c. of the mixture to 1 c.c. of chloroform, 
since the power of the mixture relative to that of chloroform is as 8 to 15. 
As a matter of fact, the 2 c.c. per 1000 solution of mixture had rather 
more effect than the 1 c.c. per 1000 solution of chloroform. 
Similarly, with a mixture of equal volumes of alcohol and chloro- 
form, in which the physiological power of the alcohol is relatively still 
smaller than in the case of ether, the action is still further reduced. 
In this case the equivalence should have been 1°97 c.c. of mixture to 
1 c.c. of chloroform. 
These observations show clearly that in anesthetic mixtures com- 
posed of ether and chloroform, or of alcohol, ether, and chloroform, 
the principal anesthetic power pertains to the chloroform, while ether 
and a fortiori alcohol act principally as diluents of fhe chloroform.” 
Thus in the well-known ACE mixture, composed of 1A, 2C, and 
3E, the shares of anesthetic power of the constituents are A=1, C=150, 
E=15, the total power of the six volumes of mixture is 166, which, 
1 June 24, 1909. 
? This is confirmatory of the statement I made in 1897 from experiments on 
isolated nerve, to the effect that ‘the action of mixtures of ether and chloroform 
(7 parts of ether to 1 part of chloroform) is additive—the sum of the action of the 
two constituents of the mixture,’ (British Medical Jowrnal, November 20, figs, 20 
and 21.) 
1909, x 
