1 The Collected Works of Sir Humphry Dary, Barf. Edited by his Brother. Vol. iii. London, 8vo. 1839.

(54) Many distinguished persons breathed the gas at Davy's wish, and recorded their experiences for his use. In these records, James Thomson speaks of 'involuntary laughter' and of the 'satisfaction felt in violent exertions of the legs and arms'; S. T. Coleridge says 'the only motion which I felt inclined to make was that of laughing at those who were looking at me' - adding that 'he could not avoid, nor indeed felt any wish to avoid, beating the ground with his feet'; Wedgwood says that he 'acted ridiculously ' and 'could not avoid doing so,' and that he had 'a very strong inclination to make odd antic motions with his hands and feet'; Thomas Pople says that he had 'an involuntary burst of laughter'; Lovell Edgeworth tells that he had 'a strong propensity to laugh' and 'did burst into a violent fit of laughter,' that he 'capered about the room,' and could not restrain himself; M. M. Coates says that he ' had an irresistible propensity to violent laughter and dancing.'

(55) The beginning of the laughter often took place, usually I think, when the breathing of the gas ceased. By several persons this is definitely recorded. Robert Southey, for instance, says: 'When I took the bag from my mouth, I immediately laughed,'and adds that 'the laugh was involuntary but highly pleasurable.' He also says that he was 'compelled to exercise his arms and feet.' J. W. Tobin says 'on removing the bag from my mouth I laughed.' He started from his chair, vociferating with pleasure, ran through the rooms of the house, and gave several blows, ' but in the spirit of good humour,' to a stranger who was present. G. C. Bedford says that 'when the bag was taken away, an involuntary though agreeable laughter took place.'

(56) It thus appears that the laughter caused by the breathing of this gas is a boisterous form of ordinary laughter. In laughter from usual causes there often occur shouting, jumping, dancing, gesticulating and throwing the arms and legs about in an altogether senseless and ridiculous way; but these things appear to occur more constantly and with more emphasis in the laughter which follows the inhalation of nitrous oxide.

Looked at with reference to its cause, this drug-laughter becomes still another kind of laughing; but, apart from its cause, it is nothing more than a form of noisy ordinary laughter.

(57) There is one point in connection with this drug-laughter which seems to me of interest and value. Almost without exception those who record their experiences of it speak of the pleasurable feelings which are caused by breathing the gas, and they often speak of the pleasure as being strong. In other words, it appears to be a laughter of happiness. Davy himself calls it a 'pleasurable delirium' and 'a delirious trance.' Coleridge calls it 'unminglcd pleasure,' 'highly pleasurable,' an ' ecstasy.' George Burnet says it is ' a lively enjoyment inconceivably pleasurable.' P. Roget says that it was 'like a half delirious dream,' that during its continuance thinking is active but delirious, and that the feelings are so agreeable as to create a longing for repeated doses. This last is a point of interest. James Thomson calls it 'a high extraordinary degree of pleasure.' Henry Wansey says the sensations were delightful, with 'highly pleasurable thrillings all over the frame.' Stephen Hammick says he had a 'sense of exhilaration' and of 'extreme pleasure.' Southey says that he felt 'unusually cheerful,' and Kinglake that he had been 'almost delirious by highly pleasurable sensations following in the train.'

This testimony to the pleasantness of the effects of breathing nitrons oxide leads me further on to suggest a possible use of the gas as a therapeutic agent

There may be a laughter which cannot easily be regarded as the expression of a joyous state of mind, but the laughter provoked by inhaling nitrous oxide, in the way Davy gave it, seems nearly always to be the expression of happy mental feelings.

(58) There are other points of interest in the records of these experiences. For instance, Davy says that, when he inhaled the gas, a candle or ray of sunlight became dazzling, that luminous points passed before his eyes, and that his hearing was rendered more acute. Others had a similar experience.

Many speak of the difficulty of describing the mental state, and say that new terms would be needed to do it well. There is frequent reference to the rapidity of the thinking. Davy says that 'highly vivid ideas passed rapidly through his mind,' and P'. Roget that 'ideas succeeded one another with extreme rapidity,' and that 'thoughts rushed like a torrent' through his mind. The ideas are often called vivid and novel, and for this reason are said by some to he 'calculated to leave a lasting impression on the memory.' But, they do not really appear to do this indeed, by almost universal consent, it was found difficult to recall the thoughts with fulness and accuracy just as happens in dream-thinking.

(59) If the state of mind, and the bodily movements, and the condition of the senses, and the con-duet, which result from breathing nitrous oxide, were to continue, instead of ceasing soon after the inhalation of the gas is stopped, I scarcely think that any one would hesitate about describing the condition as one of mental disorder - toxic of course in its origin. It would be a form of mental disorder, indeed, which would almost certainly lead to the seclusion of the person in whom it appeared, because of the trouble and discomfort he would cause to those about him. The transitoriness of the condition does not make it differ scientifically from the condition if it persisted.

(60) But the occurrence - the repeated occurrence - of such short fits of mental disorder appears to cause no injury. On the contrary, the recorded experiences of many capable observers is not only to the effect that no harm is done, but rather that the result is a benefit, if we may accept as signs of benefit a consequent sense of bodily well-being and strength, activity of mind, sound tranquil sleep, and an unusually good appetite. Sir Humphry Davy himself, in recording his numerous personal experiences, seems to me to be clear on this point, and scarcely less so are many other observers.