ABSTRACT
Some of the author's young collaborators studying conditioned reflexes have been complaining for a number of years of the drowsy state of their experimental animals, a state which hindered them from continuing their studies. This difficulty made itself felt particularly when they chose as the conditioned agent for the thermal stimulation of the animal’s skin either heat at about 45 degrees Celsius or cold of about 0 degree Celsius. The latter cases usually ended in the animal’s deep sleep and cessation of all of its complex nervous activity. If ordinary sleep is a depression, inhibition of all of the activity of the higher division of the brain, hypnosis must be regarded as a partial depression of the different portions of this division.
