Thus, in hay fever or "rose cold" the tears, the inflammation of the membranes of the nose, the cough, the other trying symptoms, all are linked with the sight of a rose, or dust, or sunlight, or some other outside fact to which attention has been called as the cause of hay fever, into a complex, "an automatically working mechanism." And the validity of this explanation of the regular recurrence of attacks of this disease is sufficiently demonstrated by the fact that a paper rose is likely to prove just as effective in producing all the symptoms of the disease as a rose out of Nature's garden. Another striking illustration of the working of this principle is afforded by two gentlemen of my acquaintance, brothers, each of whom since boyhood has had unfailing attacks of sneezing upon first arising in the morning. No sooner is one of these men awake and seated upon the edge of his bed for dressing than he begins to sneeze, and he continues to sneeze for fifteen or twenty minutes thereafter, although he has no "cold" and never sneezes at any other time. [Sidenote: _Two Classes of "Complexes"_] Obviously, if absolutely all mental experiences are preserved, they consist altogether of two broad classes of complexes: first, those that are momentarily _active in consciousness_, forming part of the present mental picture, and, second, all the others--that is to say, all past experiences that are _not at the present moment before the mind's eye_. There are, then, _conscious_ complexes and _subconscious_ complexes, complexes of _consciousness_ and complexes of _subconsciousness_. [Sidenote: _The Subconscious Storehouse_] And of the complexes of subconsciousness, some are far more readily recalled than others. Some are forever popping into one's thoughts, while others can be brought to the light of consciousness only by some unusual and deep-probing stimulus. And _the human mind is a vast storehouse of complexes, far the greater part buried in subconsciousness_, yet somehow, like impressions on the wax cylinder of a phonograph, preserved with life-like truth and clearness. Turn back for a moment to our definition of memory. You will observe that its second essential element is Recall. Recall is the process by which the experiences of the past are summoned from the reservoir of the subconscious into the light of present consciousness. We necessarily touched upon this process in a previous book, in considering the Laws of Association, but here, in relation to memory, we shall go into the matter somewhat more analytically. THE LAWS OF RECALL [Illustration: Decorative Header] CHAPTER IV THE LAWS OF RECALL [Sidenote: _The Law of Integral Recall_] Law I. The primary law of recall is this: _The recurrence or stimulation of one element in a complex tends to recall all the others._