Memory, in fact, is largely reciprocal, and when one of the parties has lost his power of response the key is gone. If the lock won't yield to the key, you are satisfied that the key is the wrong one, no matter how much it looks like the right one. I think I could tell my dog from a thousand other dogs; but if the creature were to lose his memory and to pass me in the street without answering my call, I should pass on, simply observing that he bore a remarkable likeness to my animal.
Most of us, I suppose, have experienced in a momentary and partial degree a sudden stoppage of the apparatus of memory. You are asked, let us say, to spell "parallelogram." In an ordinary way you could do it on your head or in your sleep; but the sudden demand gives you a mental jerk that makes the wretched word a hopeless chaos of r's and l's, and the more you try to sort them out the less convincing do they seem. Or walking with a friend you meet at a turn in the street that excellent woman, Mrs. Orpington-Smith. You know her as well as you know your own mother, but the fact that you have got to introduce her by her name forthwith sends her name flying into space. The passionate attempt to capture it before it escapes only makes its escape more certain, and you are reduced to the pitiful expedient of mumbling something that is inaudible.
The worst experience of a lapse of memory that ever came to me was in the midst of a speech which I had to make before a large gathering in a London hall. I had got to the middle of what I had to say when it seemed to me that the whole machine of the mind suddenly ceased to work. It was as though an immense loneliness descended on me. I saw the audience before me, but apart from vision I seemed bereft of all my faculties. If I had in that instant been asked for my name I am doubtful whether I could have got anywhere near it. Happily some one in a front row, thinking I was pausing for a word, threw out a suggestion. It was like magic. I felt the machine of memory start again with an almost audible "puff, puff," and I went on to the end quite comfortably. The pause had seemed terribly long to me, but I was surprised afterwards to find that it had been so brief as to be generally unnoticed or regarded as an artful way of emphasising a point. I let it go at that, but I knew myself that in that moment I had lost my memory.