652 Mr. F. Gallon [May 13, 



liypcrfBstbcsia aud partial autBstliesia is a frequent functional 

 disorder, markedly so among the hysterical and hypnotic, and an 

 organic disorder among the insane. The abundant facts that I have 

 collected seem to show that it may also coexist with all the 

 appearances of good health and sober judgment. 



A convenient distinction is made between hallucinations aud 

 illusions. Hallucinations are defined as aj^j^earances wholly due to 

 fancy ; illusions, as misrepresentations of objects actually seen. There 

 is also a hybrid case which depends on fanciful visions fancifully 

 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 interpretation 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, may become more consciously present, and be interpreted 

 into fantasmal appearances. Many cases, if time 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-paper and the 

 shadows of the bed-curtains, aud 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 analyse it without the recollection 

 of what took place more slowly when we were weakened by illness. 

 The first essential element in their construction is, I believe, the small- 

 ness of the area covered by the glance at any instant, so that the eye 

 has to travel over a long track before it has visited every part of the 

 object towards which the attention is generally directed. It is as with 

 a plough, that must travel many miles before the whole of a small 

 field can be tilled, but with this imjjortant difference — the plough 

 travels methodically up and down in jjarallel furrows, the eye 

 wanders in devious curves, with abrupt bends, and the direction of its 

 course at any instant dej^ends on four causes : on the easiest sequence 

 of muscular motion, speaking in a general sense, on idiosyncrasy, on 

 the mood, aud on the associations current at the moment. The effect 

 of idiosyncrasy is excellently illustrated by the "Number forms," 

 where we saw that a very sj^ecial sharply defined track of mental 

 vision was preferred by each individual who sees them. The influ- 

 ence of the mood of the moment is shown in the curves that charac- 

 terise the various emotions, as the lank drooping lines of grief, which 

 make the weei)ing willow so fit an emblem of it. In constructing 

 fire -faces it seems to me that the eye in its wanderings tends to follow a 



