THE VISIONS OF SANE PERSONS. 527 



show that it may also coexist with all the appearances of good health 

 and sober judgment. 



A convenient distinction is made between hallucinations and illu- 

 sions. Hallucinations are defined as ai^pearances wholly due to fancy; 

 illusions, as misrepresentations of objects actually seen. There is, 

 however, a hybrid case which deserves to be specifically classed, and 

 arising in this way: Vision, or any other sensation, may, as already 

 stated, be a " direct " sensation excited in the ordinary way through 

 the sense-organs, or it may be an " induced " sensation excited from 

 within. We have, therefore, direct vision and induced vision, and 

 either of these may be the ground of an illusion. So we have three 

 cases to consider, and not two. There is simple hallucination, which 

 depends on induced vision justly observed ; there is simple illusion, 

 which depends on direct vision fancifully observed; and there is the 

 hybrid case of which I spoke, which depends on induced vision fanci- 

 fully observed. The problems we have to consider are, on the one 

 hand, those connected with induced vision, and, on the other hand, 

 those connected with the interj^retation of vision, whether the vision 

 be direct or induced. 



It is probable that much of what passes for hallucination proper 

 belongs in reality to the hybrid case, being an illusive interpretation 

 of some induced visual cloud or blur. I spoke of the ever- varying 

 patterns in the field of view ; these, under some slight functional 

 change, might easily become more consciously present, and be inter- 

 preted into phantasmal appearances. Many cases, if space allowed, 

 could be adduced to support this view. 



I will begin, then, with illusions. "What is the process by which 

 they are established ? There is no simpler way of understanding it 

 than by trying, as children often do, to see " faces in the fire," and to 

 carefully watch the way in which they are first caught. Let us call to 

 mind at the same time the experience of past illnesses, when the listless 

 gaze wandered over the patterns on the wall-j^aper and the shadows 

 of the bed-curtains, and slowly evoked faces and figures that were not 

 easily laid again. The process of making the faces is so rapid in health 

 that it is difficult to analyze it without the recollection of what took 

 place more slowly when we were weakened by illness. The first es- 

 sential element in their construction is, I believe, the smallness of the 

 area upon which the attention is directed at any instant, so that the 

 eye has to move much before it has traveled over every part of the 

 object toward which it is directed. It is as with a plow, that must 

 travel many miles before the whole of a small field can be tilled, but 

 with this important difference the plow travels methodically up and 

 down in parallel furrow&; the eye wanders in devious curves, with ab- 

 rupt bends, and the direction of its course at any instant depends on 

 four causes : on the most convenient muscular motion in a general 

 sense, on idiosyncrasy, on the mood, and on the associations current at 



