Professor Wyllie tells me that he thinks the laughter of the negro very characteristic, and another good observer tells me that there arc twenty of his friends and more with a special laughter which he easily recognises; that is, he knows by the laughter who is laughing.

There is not only a difference in the forms of laughter, both in individuals and in races, but there is a difference also in the things which cause laughter. As regards individuals this is so great, that in Goethe's opinion men show their character by nothing more clearly than by what they consider 'laughable'

(27) I have not yet given any definite name to the particular state of mind which has its expression in laughter. It is commonly regarded as a joyous and merry state. But other and very different states of mind give rise to laughter. From some of them, indeed, everything of the nature of joy or merriment is either wholly absent or is very obscurely present.

(28) A consideration of the causes of laughter is an extremely complex subject, because they are so numerous and so different in their nature, and they cannot be disclosed, in my opinion, by any direct and separate discussion of each alleged cause. Their number, nature, and variety can, I think, be best shown by treating the subject as a whole.

(29) Perhaps the commonest cause of laughter, as Darwin says, is the perception of 'something incongruous, exciting surprise and some sense of superiority in the laugher.' This cannot, however, be accepted as unalloyed joyousness. Indeed, the pleasantness so caused must often be of a character which should make us unwilling to acknowledge that we had felt it, and perhaps make us ashamed.

(30) The causes of laughter are not the same in childhood and in adult life. Many of the things that bring laughter to a boy or girl have no such effect on adults. This is true, however, of the other expressions of mental states. For instance, bodily pain excites children to cry and weep, but weeping with adults is 'almost confined to mental distress.' Children, however, must be some months old - three or four at least - before pain brings tears. They cry when in pain at an earlier age. Indeed they cry or scream, probably from pain or discomfort, immediately after birth, to their advantage, but no tears follow crying till they are about three or four months old, after which time crying and weeping, in child life, become interchangeable words,

It is true of all expressions of emotion or mental feeling that they change with age, and that some of them altogether cease to be manifested in late life. We may reach an age when we are no longer able to join in laughter, but we should make an effort to carry youth in this matter, and in many others, as as far as possible into advancing years. I say this, notwithstanding the opinion I have expressed as to the cousinship between laughter and insanity, because I have regarded such insanity as only a healthy dishealth of the mind.

(31) Laughter may be, at its root and in the main, an expression of joy and happiness. It is certainly so spoken of by the multitude. But it also expresses other states of mind. If these other states contain any form of happiness, we seldom speak of that form with respect. What I desire here to emphasise is that very different states of mind are expressed by laughter. So that, if it be a puzzle why the muscles of the chest and face should involuntarily and instinctively go into convulsions to express a happy and joyous state of mind, the puzzle is deepened, when it is found that the very same muscular commotion may be the expression of scorn, vanity, or superciliousness.

It is possible, of course, that the physical phenomena may not in all kinds of laughter be identical. The differences may not be easily seen. Nevertheless they may exist. Indeed, it has been asserted that the sounds of the laughters of joy, scorn, contempt, and vanity can be distinguished from each other. And it is also conceivable that the muscular commotion in laughter from one cause may not be exactly the same as that in laughter from another cause, but as yet no one has attempted to give a description of such differences. Their existence rests on loose assertion, yet it is possible that they exist.

There is one thing, however, which renders their existence improbable, namely, the fact that both the convulsive movements and the sounds which attend laughter from tickling are beyond question the same as those which attend laughter from known pleasant mental feelings. Yet the causes of these two laughters may be said to be as wide as the poles asunder. It does not bring the two into closeness to call the first a tickling of the mind. To do so may be a pretty conceit, but it is nothing more.

The whole subject presents itself as a set of puzzles within puzzles. Why such irrational, senseless, and purposeless movements and sounds should express a state of joy or any other special mental feeling passes comprehension. It puts the matter into a, deeper darkness when we find the very same phenomena produced by mechanically tickling the armpit or the sole of the foot.

Common-sense can scarcely fail to pronounce the man, who, from any cause, is laughing boisterously, to be a ridiculous object, behaving irrationally. He utters sounds without meaning, throws himself into contortions without purpose, and expands and wrinkles his face till he is barely recognisable. He is acting insanely - and it does not affect this view of his conduct and condition to say that he is the better and not the worse for it.

(32) It is quite necessary to remember that any idea or scene, in order to be ludicrous, must not be of grave import. It must not be of a momentous nature. There must be no appearance in it of danger or great suffering. Over things of great importance joy is always silent. Neither laughing nor smiling follows. 'No poor man would laugh or smile on suddenly bearing that a large fortune had been bequeathed to him.' His heart might be full of joy, but that would not be expressed by laughter. There are joys that are even solemnising, and we arc never graver than when experiencing the highest pleasure we know. Great happiness never manifests itself by a burst of laughter, and the highest enjoyment of wit has no recognised bodily sign.