EXCITATION AND CONDUCTION 69 
hydrate solution is compared in the usual manner with 
that of a normal nerve, it is easily demonstrated that the 
carbon dioxide production of the nerve so treated is 
‘greatly increased. The quantitative determinations 
tabulated above illustrate this perhaps more con- 
vincingly (see Table IX, horizontal column 3). 
That this change in the carbon dioxide production of 
the nerve when treated with the lower concentration is 
closely connected with the physiological state is further 
demonstrated in the following experiments. Many claw 
nerves were isolated from several spider crabs, each 
pair chosen being approximately of the same weight, and 
of each pair one was placed in a 0.4 per cent solution of 
chloral hydrate and the other in sea-water. A compari- 
son was made of the rate of carbon dioxide production 
of the first pair in the biometer in the usual manner at 
the end of ten minutes; at the end of half an hour a 
second pair was compared similarly, and so on. The 
result is given in Table IX. This table is of more than 
passing interest, for it illustrates an easy source of error 
in the study of narcosis. Evidently it is of prime 
importance to determine the carbon dioxide output 
during a comparatively small time interval, rather 
than during one of long duration. If we were to deter- 
mine the output of the gas for sixty minutes’ respiration 
of the nerve treated with a 0.4 per cent chloral hydrate 
solution, we might be led to the conclusion that the 
narcotic has no effect whatever on the metabolic rate. 
For although we have shown, by taking corresponding 
nerves at the beginning and at the end of the narcosis, 
that the primary effect is to increase carbon dioxide 
production and that later it is greatly diminished, the 
