The question, then, is: How do anesthetics, as these things are called, stop the working of the brain? Such an anesthetic as chloroform is made up of certain chemical molecules. When chloroform is breathed these molecules pass into the substance of the brain itself. There the chloroform molecules combine with the molecules of the brain, probably with the result that the brain can no longer use up the oxygen in the blood, and so has to stop working. But as soon as the person stops breathing chloroform his blood going to the brain becomes free of it. The chloroform then passes back from his brain into the blood, and is breathed away by the lungs, going back the same way it came, and the person becomes conscious again.
The effect chloroform generally lasts about 1 to 2 hours, but it really depends on the individual as well as on the dosage.