168 ON ANAESTHETICS 
arrangement as near the lower limit of efficiency as was possible. And as there 
is no special virtue in flannel, as compared with a single layer of linen of coarse 
texture, I substituted for the frame and flannel the corner of a towel, pursed up 
systematically into a concave mask to cover the mouth and nose by pinching 
it together at such a distance from the corner that, when the pinched-up part 
is held over the root of the nose, the corner extends freely to the point of the chin. 
The cap formed in this manner being so arranged upon the face, chloroform 
is gradually dropped upon it till the greater part of it is soaked, the edges being 
left dry to avoid irritation of the skin by the liquid; and the moist condition 
is maintained by frequent dropping until the requisite physiological effects are 
produced ; the respiration being at the same time carefully watched with a view 
to the instant adoption of the measures described at p. 144 in case of any 
obstruction to the free entrance of air. When full anaesthesia has been pro- 
duced, it is steadily maintained by dropping with about half the frequency : 
for I find that half the quantity of chloroform per minute that is used for pro- 
ducing anaesthesia is not far from the amount required for maintaining it. 
Any one accustomed to giving chloroform with the folded towel or compress 
has to learn to avoid the two extremes of applying the drop-bottle too seldom, 
and putting on too much chloroform at a time. 
In giving chloroform in this manner, it is of great importance to bear in 
mind that the amount inhaled is proportioned to the surface which is moistened, 
so that it would not be right to use an indefinitely large piece of towel for the 
purpose. When the cap is made as above directed, large enough to extend 
freely from the root of the nose to the point of the chin, the part which is mois- 
tened during the production of anaesthesia has an area of about nine square 
inches (that of a circle three and a half inches in diameter) in the case of the 
adult male. But the apparatus is self-adjusting in so far that the cap varies 
in dimensions with the face, which, again, is more or less proportioned to the 
size of the body; and thus, for example, a very much smaller evaporating 
surface is provided for a young child than for an adult. It is further self-regu- 
lating in this respect, that when the breathing is shallow, and the quantity 
of air to be mixed with the chloroform consequently diminished, the percentage 
of the chloroform is not correspondingly increased, because a much smaller 
amount evaporates under those circumstances than when the air is moved 
freely over the cloth in deep inspiration ; and further, when the vapour is not 
drawn into the chest, its density causes it to flow away under the loose margins 
of the cap, instead of accumulating as it would do under a closely fitting bag. 
When the surface of the towel is restricted as above recommended, the 
proportion of chloroform to the air inhaled is extremely small. In order to 
