PRESIDENTIAL ADDRESS. 661 
500 c.c. carries 20 c.c. of chloroform vapour into the lungs. Of this 20 c.c, it is 
no exaggerated estimate to take one-half, or 10 c.c., as absorbed by the pulmonary 
blood, the other half being expelled in the expired air. If the subject breathes 
twenty times per minute 500 ¢.c. at each inspiration, his blood absorbs 206 c.c. of 
chloroform vapour in one minute—i.e., one gramme of fluid chloroform. He may, 
of course, absorb less than one gramme per minute; but he may also absorb more. 
Snow estimated that 17 minims of chloroform in the blood (7.e., about one gramme) 
was sufficient to produce anzsthesia, while double the amount was fatal. 
Grehant found that after death by chloroform the blood contained half a 
gramme of chloroform per litre of blood—i.e., five litres of blood, which is the 
normal amount in an average man, would contain two and a half grammes. 
Buckmaster and Gardner find from numerous experiments results that may be 
summarised as follows :— 
Quantity of chloroform (in grammes) contained in 100 grammes of blood :— 
Min, Mean. Max, 
Taken during deep anesthesia. . 0:020 0:030 0-040 
Taken after death by anzsthesia . . 0:040 0:050 0-060 
These results signify in five litres of blood between one and two grammes as the 
anzesthetic amount, between two and three grammes as the lethal amount. 
Consider, then, what might happen if a patient were to absorb chloroform at 
anything like the rate of one gramme per minute, and what might happen if by 
mischance he should absorb two or three grammes in a fraction of a minute. This 
is a mischance that can occur in the ordinary method of inducing anesthesia: a 
few deep gasps by a struggling patient, a few moments’ inattention on the part 
of an administrator, and the blood almost at once be fatally overloaded with 
chloroform, 
In the early days of chloroform anesthesia it used to be considered admissible 
to administer chloroform vapour of 4 and 5 per cent. strength in air; but at that 
time the means of estimating percentage were very imperfect, and the figures 
quoted were little better than guesswork. 
The dictum of the Edinburgh school was ‘ plenty of chloroform with plenty 
of air by continuous administration.’ 
Some ten years ago, at a meeting of the Society of Anesthetists,’ I pleaded 
for the continuous administration of chloroform vapour at a strength (in air) of 
not below 1 per cent. and not above 2 per cent., which amounted to a translation 
into figures of the Edinburgh dictum, with justification of the figures by 
quantitative observation. Perhaps I may briefly explain the method? by which 
the percentages of chloroform and air are obtained :— 
Grammes 
A litre, or 1,000 ¢.c., of chloroform vapour weighs . » bfado 
A litre, or 1,000 c.c., of air weighs . ; ; “ . 1288 
The litre weight difference is therefore . - . . 4045 
The weight difference of 1 ¢.c. is approximately 4 milligrammes. 
So that a 100 c.c. flask in which 1, 2, 3, &c., c.c. of air are replaced by 1, 2, 
8, &c., c.c. of chloroform vapour is 4, 8, 12, &c., milligrammes heavier than the 
same flask filled with air. 
So that added weights of 4, 8, 12, &c., milligrammes indicate 1, 2, 3, &c., per 
cent. of chloroform vapour present. 
Thus, by simply counterpoising a 100 c.c. flask (or, preferably, a 250 c.c. bulb, 
as to give weight increments of 10, 20, 80, &c., milligrammes as indications ot 
1, 2, 3, &e., per cent.) filled with air against a similar bulb filled with chloroform 
mixture, the percentage of the mixture is read directly by the number of centi- 
grammes required to counterpoise. For instance, a bulb full of mixture being, 
1 Waller, British Medical Journal, April 23, 1898. 
2 Waller and Geets, zbid., June 20, 1903. 
