The fact that failure of memory by no means proves the absence of dreaming may be illustrated, not only by the forgetfulness of what takes place during hypnotic sleep, but by what we sometimes witness during partial anaesthesia maintained by drugs. This was well shown in a case I was once concerned with, where it was necessary to administer chloroform (preceded by the alcohol-chloroform-ether mixture) for a prolonged period during a difficult first confinement. The drug was not given to the point of causing complete abolition of mental activity, and the patient talked, and occasionally sang, throughout, referring to various events in her life, from childhood onwards. The sensation and the expression of pain were not altogether abolished, for slight cries and remarks about the discomfort and constraint imposed upon her were sometimes mingled in the same sentence with quite irrelevant remarks concerning, for instance, trivial details of housekeeping. Confusions of incompatible ideas also took place, as during ordinary dreaming. 'Where is the three-cornered nurse,' she thus asked, 'who does not mind what she does?' There was also the abnormal suggestibility of dream consciousness. The questions of bystanders were answered but always with a tendency to agree with everything that was said, this tendency even displaying itself with a certain ingenuity as when in reply to the playful random query: 'Were you drunk or sleeping last night?' she answered, with some hesitation: 'A little of both, I think.' To the casual observer, it might seem that there was a state of full consciousness on the basis of which a partial delirium had established itself. Yet on recovery from the drug there was no recollection of anything whatever that had taken place during its administration, and no sense of the lapse of time. Fantastic and marvellous as our dreams may sometimes be, they are in practically all cases made up of very simple elements. It is desirable that we should at the outset have a provisional notion as to the sources of these simple elements. Most writers on dreams hold that there are two great sources from which these elements are drawn: the vast reservoir of memories and the actual physical sensations experienced at the moment of dreaming, and interpreted by sleeping consciousness. Various names have been given to these two groups, the recognition of which is at least as old as Aristotle.[10] Thus Sully calls them central and peripheral, Tissié, psychic and sensorial, Foucault, imaginative and perceptive. Fairly convenient names are those adopted by Miss Calkins, who calls the first group representative, the second group presentative, meaning by representative 'connected through the fact of association with the waking life of the past,' and by presentative 'connected through sense excitation with the immediate present.'[11]