FEELINGS OF RESPIRATION. 129 their action, must be reckoned as a condition of healthy respiration. The feelings of Respiration, both pleasurable and painful, are well marked. They include the gratification of pure air enhanced by the increased action due to muscular exercise; the various shades of oppression from over-crowded rooms and unwholesome gases, and the distressing experience of suffocation; besides the pains attendant on the many diseases of the lungs. 8. The influence of pure and stimulating air abundantly inhaled, spreads far and wide over the system, elevating all the other functions by the improved quality imparted to the blood. The indirect consequences do not altogether hide the grateful sensibility arising from the lungs themselves, and referred by us to the region of the chest; a sensation not very acute or prominent, but possessing that choice and well known quality, expressed by the term 'freshness,' or 'refreshing.' This quality manifestly implies a contrast; for it is most strongly felt when we pass from a lower to a higher degree of aeration. No technical nomenclature can increase the conception possessed by every one of this remarkable sensibility; but for the sake of comparison with the other parts of our mental constitution, an attempt at verbal description is necessary. The main feature of the description turns upon the contrast of the greater activity of the lungs with an immediately preceding activity of an inferior degree; and we derive here an example of a class of feelings not as yet dwelt upon in our exposition-the feelings of relief,-where the entire force of the sensibility rises out of the change from a state of pain or oppression to its opposite, or from a feeble to a powerful stimulus. It may be doubted whether much feeling resides in the lungs, after a given pace has been established for a length of time, but any acceleration of the rate of exchange of the two gases (by no means depending altogether on the rate of breathing) does for a time yield that delightful freshening sensation, which tells so immediately on the mental system as a contribution to our enjoyment, and a K stimulus to our activity and desire for rural recreation and bodily exercise. 9. The feelings of insufficient and impure air are manifested in the forms of faintness, sense of exhaustion and weariness, and are doubtless due not to the lung-sense alone, but to the lowered condition of the body at large. The characteristic sensibility of the lungs is manifested in the state termed suffocation, which will sometimes manifest itself clearly in the midst of a complex mass of other painful sensations. It is this state, therefore, that we must now particularly allude to, as perhaps the true foundation of the forenamed sensibility of freshness, seeing that this last is a feeling of relief. Suffocation is felt in the absence of air, as in drowning, in an atmosphere deteriorated by poisonous gases, such as chlorine or sulphurous acid, in attacks of asthma, and in voluntarily holding in the breath. After holding the breath for fifteen or twenty seconds during ordinary respiration, or forty seconds after a deep respiration, there arises an insupportable sensation over the whole chest, concentrated under the sternum, and no effort can maintain the interruption of the respiratory acts. This urgent sensation of want of breath when carried to its full extent by any mechanical impediment to the aeration of the blood is one of the most painful and oppressive kind, and is referable to the pulmonary plexuses (of nerves) distributed to the bronchia, and perhaps on the walls of the lobular passages and cells. The impression made on these peripheral nerves by the absence of oxygen, and the undue presence of carbonic acid in the air in contact with them, is propagated to the spinal cord and medulla oblongata by the sympathetic and vagus, and there excites those combined actions of the muscles of inspiration which lead to the renewal of the air.'* This sensation, so painful, intense, and keen, is aggravated, in the extreme cases, by the circumstance of growing worse every moment until relief or rupture ensue. It may rank as the most unendurable of all *Todd and Bowman, ii. 403. SENSATION OF COLD. 131 human sensations; while the fact that causes it, is the most dangerous to human life of any that can occur. The pain fulness of the sensation would suffice to set on a train of voluntary actions, and to prompt the most urgent desires for relief; but this is not entirely left to the will, for the reflex nervous system is powerfully called into play on the occasion. This reflex action consists, as above stated, in an increased stimulus of the respiratory muscles; which however is not in all cases the thing demanded. When the suffocation arises from some pungent odour, the reflex stimulus is a mistake, and we must overpower it by the voluntary effort of holding the breath for a time, till we have got out of reach of the mischief. In the suffocation of a crowded room, the increased action is appropriate: like the accelerated breathing of consumptive patients, this compensates for the small quantity of oxygen gained by a single breath. 10. The present appears to me not an inappropriate place for bringing in the important feelings of Cold and Heat, whose description is not to be omitted among our Sensations. Under the sense of Touch, these feelings have to be adverted to as a certain class of sensations of contact with the skin; here we propose to deal with them as affecting the body throughout. To commence with Cold. The outward cause of this feeling is some influence tending to lower the temperature of the body. The natural heat of the blood is about 98°, and any contact below this point feels cold: any contact above it feels warm. There is a certain surplus heat generated in the human system, which enables us to live in a medium below 98°, without feeling cold, and if this heat be husbanded by clothing, a very great depression of external temperature may be endured. A room is warm at 60°. The outer air can be endured at freezing and far below, either by means of exercise, which evolves heat, or of clothing, which retains it. An acute cold acts like a cut or a bruise, injuring the part affected, and producing intensely painful sensations of the same class as arise from violent local injuries. The tempe rature of freezing mercury would destroy the skin, like boiling water, or a sharp cut. This case needs not any special discussion at the present stage. The proper sensation of Cold arises from a general cooling of the body, or any considerable part of it, below the point suitable to healthy action. The term 'chillness,' expresses the fact precisely. How this cooling operates upon the various tissues, upon the circulation, and the different nutritive functions, I am not distinctly informed. We may safely infer, that the vital activities are impaired by it in some way or other-that it makes the blood to stagnate, suspends or vitiates the secretions, lowers the tone of the nerves-in short, deranges the organic processes, like disease or insufficient. nutriment. No doubt the mode of derangement is something distinct, for I scarcely know any other action that can imitate the sensation of chillness, although such there may be, just as there are derangements that appear to imitate the effects of too great heat. The feeling or sensation of chillness has a well-marked character, and a generical distinctness. It is as a general rule of the painful class, being not acute but massive and powerful, and strongly felt. Our body appears as if very raw and sensitive in the matter of temperature. The feeling of cold engrosses the sensibility of the frame; we find a difficulty in keeping the attention upon anything else. It has not the unendurable character of acute pains, nor the terrible influence of suffocation; nor can it rank with nervous depression unless intense enough to produce that special effect. But it can neutralise many pleasures; neither rest in fatigue, nor food in hunger, can satisfy a frame very much chilled with cold. The imagination can scarcely picture any satisfying scenes of enjoyment; the entire world seems comfortless. The expression of cold is chiefly the physical action of shivering, arising from its influence on the nerves; occasionally, too, there is hysteric laugh; beyond these there is nothing specific or different from the other forms of depression. The activity suggested is of course to get warm by some means or other; but the influence of the state is often paralysing to exertion. SENSATION OF HEAT. 133 In regard to the permanence of the impression, or the power of reviving in idea a state of depressing chill, although like all the other organic sensations, it is difficult to realize when not felt, yet the abiding impression is quite sufficient to induce constant and extensive precautions against this disagreeable condition. I have said above, that there are pains that are very much neglected when once gone, and I gave the case of nervous exhaustion as an example; but this is by no means true of cold. Of all the disagreeables hitherto treated of, this one seems to me to rank very high in the estimate of precautionary prudence, which is the strongest proof either of its endurance as an idea, or of its reality being always so close upon us as never to be long out of mind. There is a secondary action of chillness, which alters considerably the character of its sensation. Cold is a stimulant of nervous action, and provokes an increased activity of the lungs and the circulation; also inducing bodily and mental exertion. When not too great, the stimulus is a wholesome and invigorating one, and heightens the powers of life, and all the sensations of energy and vitality. Hence the influence of cold air, cold climates, and cold water in sustaining the tone of the human constitution. The sensation of cold is not altered, but other states are induced which cause it to be no longer an object of revulsion and dread. 11. The consequences of Heat are in nearly every particular exactly the opposite of those now stated. Acute or intense heats agree with intense colds in being simply destructive and painful. Within the point of injury to the tissues, heat is a pleasurable sensation. The pleasure of heat, like the pain of cold, is both massive and keen. There is, however, a noticeable distinction of cases, some distinguished by intensity, and others by quantity; indeed, this distinction of quantity and intensity, used all through this work as a part of the description of conscious states, has its perfect type in the case of temperature, there being a physical reality corresponding to the mental fact. Sometimes we have great intensity and small quantity, as in the scorching rays of a fire, or a cup of hot tea at other times we have large quantity with low |