(5) Then I advance a step and say, that if it would be correct to say this in regard to a fit of laughter which had lasted for a considerable time, it follows that it would also be correct to say it in regard to a fit which had lasted only for moments or minutes. Scientifically the fits are the same. Duration only has varied.

(6) If I am right, this would practically mean that there may be a frequent occurrence of short periods of mental disorder, which are not accepted as having any bad effect. On the contrary, their effect is believed to be good, and it is so regarded, even when the laughter is boisterous and immoderate.

(7) But is it possible - is it conceivable - that there can be a state of mental disorder, which occurs often in short transient attacks, and which does good and not harm ? .

In dream-thinking, which is of the nature of delirium, I have already endeavoured to show that something of this kind is possible and does occur. I do not see how we can escape from that conclusion as regards dreaming. Laughing may show mental disorder somewhat less clearly, yet I am surely right in thinking that sonorous, convulsive, uncontrollable laughter, as we see and hear it, has at least the look of a manifestation of disordered mental action; and when I add that it is certain that no one can think or speak coherently or rationally during its actual continuance, the semblance passes into reality. There is no disease about that reality, and therefore we are not hurt. So it comes, as I see the matter, that the mind may at times act passingly in certain disordered fashions, which are not pathological, which are without injury and probably beneficial. If I am right in this, it seems to follow that it is not an advantage to be always quite sane. Beyond question we get strength of mind from dreaming, which is mental disorder, and nearly as much beyond question we get strength of mind from laughing, which is almost as clearly a state of mental disorder.

(8) I turn to speak of the kind of laughter which is excited by touching certain parts of the body in a certain way. The touch must be light, and must pass quickly from one spot to another. Steady pressure or firm rubbing does not tickle, and does not cause laughter. Some persons are more easily tickled than others, so much so that even approaching them with an apparent intention to tickle causes them to laugh, and this is a curious fact in the study of the subject, since it seems to show that laughter from tickling can occur without any actual tickling. There is another curious fact which presents itself in the study of this kind of laughter, namely that persons, young and old, are often unable to tickle themselves, and never can do it so readily as it can be done by others. Still another curious thing arises from the absence of any satisfactory explanation of what gives the peculiar sensibility to the parts of the skin which can be most easily tickled. These parts are the soles of the feet, the armpits, the front of the neck, the legs just above the knees, the nostrils, and the entrance to the ears. They are thus widely spread over the body, and are not in any special or clear manner related to each other.

(9) The boy who laughs, on seeing or hearing something ludicrous, does so as the expression of a certain state of mind, which is excited through the eye or the ear. The same boy's laughter as he reads Harry Lorrequer, when nothing reaches his brain through these organs of sense, has exactly the same origin, for he is practically hearing Lever speak and seeing what Lever describes.

The mental feelings which lead to laughter usually come through sight or hearing. They may come, however, though very rarely, through taste, smell, or touch. I think it has been well established that they may possibly come through any of the senses.

The mental feelings referred to are commonly believed to be pleasant. The laughter which they provoke is regarded as the expression of a joyous and merry state of mind.

(10) The continuance of this kind of laughter is desired. It ought naturally to be so, if the view as to its being an expression of mental pleasure is correct. It is quite different with the laughter caused by tickling. Every one who is being tickled desires to put a stop to it, and does so if he can. No one invites tickling, or wishes it to be continued. It makes him laugh, but he does not enjoy the laughter, nor does he wish it to continue.

(11) But the laughter of a boy who is being tickled has the same physical characters as that of a boy who is reading Huckleberry Finn. If the laughter is heard from a room adjoining that in which the boy is, it cannot be told whether his feet are being tickled, or he is listening to Mark Twain's comic talk, or looking at the funny scenes which that talk pictures.

(12) If there are two boys in the same room, one of them having his feet tickled and the other reading this amusing boy's-book, and both laughing noisily and heartily, one great difference between the two will be apparent. The boy whose feet are being tickled will be seen struggling to get free of the tickling, while the boy who is reading the funny story-book will go on reading, and court a continuance of the laughter which it provokes.

The physical phenomena of both laughters, however, will be the same. Both may be loud and tumultuous, and both have been fairly well described as ' convulsive merriment.'

(13) But it may reasonably be asked whether there can be any true merriment in what one of the boys so resolutely struggles to prevent. Is there any real pleasure, which we wish neither to experience nor to prolong? Yet if the two laughters express different mental states, then two different, if not opposite, states of mind would be expressed in exactly the same way, and that way remarkable and emphatic. Again, if the laughter from tickling is not the expression of any particular state of mind, but is a mere reflex, then the bodily expression of a state of mind - usually regarded as a joyous state-would be the very same as the outcome of an ordinary pain-giving reflex, though the phenomena are almost startling in their character and complexity.