68 A CHEMICAL SIGN OF LIFE 
this narcotic on the weight of the tissue shows that a 2 
per cent concentration has but little effect for the first 
ten minutes, though during the course of half an hour a 
gain of 5o to 100 per cent takes place. A 3 per cent 
concentration produces a gain of 25 per cent in ten min- 
utes, while in a 4 per cent solution the nerve gains 50 
per cent in the same space of time. These results, 
together with those on the frog’s nerve, indicate that, 
whatever interpretation we put upon this change in 
weight, the result of such a process is temporarily, at 
least, to increase slightly the amount of carbon dioxide 
evolved, and that, so far as' the effects of narcotics are 
concerned in our work, its slightly increased production 
from the narcotized nerve which gains in weight may be 
looked upon as adventitious. The correctness of our’ 
interpretation of the diminution of carbon dioxide output 
as an effect primarily connected with narcosis is further 
supported by a study of the effects of weak concentra- 
tions of narcotics for different periods of time. 
Effects of weak concentrations of narcotics on carbon 
dioxide production in the nerve fiber —It is well known 
that the primary effect of narcotics is to increase irri- 
tability, after which the typical depression follows. 
This primary effect is well brought out by the use of 
rather weak concentrations of narcotics. Although 
we have made no quantitative determination of the 
degree of irritability, it is evident that a nerve after ten 
minutes’ immersion in a 0.4 per cent chloral hydrate 
solution has become abnormally irritable. After about 
one hour’s treatment, however, the nerve finally becomes 
paralyzed. If the carbon dioxide output of a nerve 
treated for ten minutes with a o.4 per cent chloral 
