There are two qualities of nervous tissues (possibly of all living tissue) that are basic in all nervous and mental processes. They are dependent upon the modificability of nerve cells and fibers by stimuli, e. g., a light flashing through the pupil and passing along the optical tracts to the occipital cortex produces changes which constitute the basis of visual memory. Experience modifies nervous tissue in definite manner, and SOMETHING remembers. Who remembers? Who is conscious? Believe what you please about that, call it ego, soul, call it consciousness dipped out of a cosmic consciousness; and I have no quarrel with you. Memory has its mechanics, in the association of ideas, which preoccupied the early English psychologists and philosophers; it is the basis of thought and also of action, and it is a prime mystery. We know its pathology, we think that memories for speech have loci in the brain, the so-called motor memories in Broca's area.[1] We know that a hemorrhage in these areas or in the fibers passing from them, or a tumor pressing on them may destroy or temporarily abolish these memories, so that a man may KNOW what he wishes to say, understand speech and be unable to say it, though he may write it (motor aphasia). In sensory aphasia the defect is a loss of the capacity to understand spoken speech, though the patient may be able to say what he himself wishes. (It is fair to say that the definite location of these capacities in definite areas has been challenged by Marie, Moutier and others, but this denial does not deny the organic brain location of speech memories; it merely affirms that they are scattered rather than concentrated in one area.) [1] Foot of the left or right third frontal convolutions, auditory speech in the supramarginal, etc. In its widest phases memory alters with the state of the brain. In childhood impressibility is high, but until the age or four or five the duration of impression is low, and likewise the power of voluntary recall. In youth (eighteen-twenty) all these capacities are perhaps at their highest. As time goes on impressibility seems first of all to be lost, so that it becomes harder and harder to learn new things, to remember new faces, new names.